Upgrading Entire System...please help

This is my first time posting, so please bear with me through my the questions. I currently have a pretty modest system. NAD C320BEE Int Amp, the associated CD Player (C520BEE I think) and an old pair of Spica TC-50's. While this system sounds alright I find myself wanting more. I recently listened to a relative’s stereo and was blown away. Granted, his system must have cost over 100k, but it gave me a taste of what is possible. The speakers literally "disappeared" and the performance was right in front of me. I was able to pin point each instrument in the sound stage and hear the most minuscule detail. It felt as if it was truly a live performance in the listening room. It was remarkable!

I have decided I that I want to upgrade, I do realize that I probably can’t even come close to the system I heard, but hopefully an upgrade will provide me with a better listening experience than what I have now. My total budget is about 5-6k. My question is this...as someone without much experience; at what price point will I start to notice significant differences in my system? Will a new $6,000 system sound audibly different to what I have now?

Second, in terms of budgeting, I want to keep things simple. A CD player, Integrated Amp (I figure in my price range this is the way to go) and speakers. I do not need a phono inputs, balanced inputs, etc. Also I would prefer solid state components. I figure a good budget would be about 1k for CD Player, 1.5 - 2k for Amplification and 2-3K for speakers.

After reading many reviews and doing research, while gaining a lot of insight, it has also made me more confused as there are seemingly infinite brand/combination possibilities in this price range. I realize it would be best to actually go to stores and listen, but how do you compare so many possibilities when certain dealers only carry certain brands?

Please give me some advice on a good place to start. It seems as though the best CD player to be had for less than 1k is the Rega Apollo. So let’s forget that for now. The amplification options are endless. I’ve complied a short list of models that interest me within my price range...

Naim Nait 5i
SimAudio i-3
YBA Design YA201
Portal Audio Panache
Arcam Diva A90
Cambridge Audio 840A

Then comes the daunting task of choosing speakers, as there seems to be even more possibilities within the 2-3k range! Also, how do I go about “matching” amplification to speakers? Maybe someone can guide me from here. Sorry for the long post, thank you for reading and I look forward to your responses!
I think you can do extremely well for 6 K especially second hand. I would not worry about CD or Amplifier except to get the features you want and at a good bargain price (second hand - so just keep an eye out - use audiogon bluebook). Speakers have a much greater impact - I would choose these carefully for 3 K second hand you can get some great quality speakers, if you are prepared to be patient and don't mind too much about aesthetics (black ash instead of expensive fine quality wood veneers).

If you are worried about amplifier matching then try to get active speakers...these are well known to sound slightly better than their passive equivalent, are common in pro use and are gaining acceptance slowly in comsumer circles.
You could call audio stores and ask them to put together a system in your price range(assuming you have all the money now) and see how you like it. I would not make a decision right away after the audition. I have been upgrading my system recently, and I started at the front end. The advantage and enjoyment of doing it this way is that as you improve your front end, you improve your speakers at the same time. I'm getting close to speaker replacement, and I'm thinking that I would have to be able to try them at home. Some of my upgrading was out of need. I blew an amp, lost connectors on another amp, hum developed on my preamp, speaker cables blew up two other amps, some interconnects shorted out, and I lacked a proper cd player. I started by getting a conservative choice of turntable(circa 1992 fully kitted Linn Sondek with Mana Sound Table) then an amp to replace a blown amp, then cables that didn't blow my amps or short out(getting advice from Plato about what cables work well with my amps). I didn't believe in cd, but Alex of APL Hi-Fi proved to me that cd can be a viable source, so I got one of his players. I used various isolation devices. When my preamp developed a hum, I brought one home to audition in my system and bought it. I believe the Rega is the choice at the price range you mention. I had it much harder, as I had trouble handling cd, and my cd player was designed with analog in mind, and compared to analog(Alex has a DAC, which could be combined with a cheap transport). Of the amps that you mention, the newest Naim Nait has had favorable mentions, but might limit your speaker choices due to power limitations. And it is expensive. My speaker budget limits my choices(maybe Revel, or Dali-both liked by the audio press). Don't forget wires, tweaks, and room acoustics. Cheap wires like Speltz anti-cables have had good press. I personally like Oritek X-2 interconnects a lot(He makes a DAC also.). Cheap power cords would include Volex 17604. Cheap isolation might be myrtle blocks with isonodes(BSA) under them. There are cheap racks(Adona,?),cheap room acoustic treatments, cheap speaker stands or supports(spikes?). I was really blown away by the difference dedicated lines made to my system. Here on Audiogon, JsaWhitlock, does dedicated lines. I'm sure that expensive system you heard has dedicated lines. Part of the enjoyment that I get from upgrading has to do with changing one thing and seeing the effect that it had on my system. But there is an advantage of the whole system done by the dealer approach-no expensive mistakes!
I want to add an addendum to the above. To get an idea of class D amps, add the Nuforce Ia-7(with V-2 boards) to the audition list. Naim should be used with their own power cords and interconnects, I believe. Separate power cords from signal cords. You can try lifting signal cords(and maybe power cords)up from the floor(I used styrofoam cups from the Dollar Tree-not the best, but cheap to try.). The reason I mention these cheap tweeks is two-fold. One, many can be done now, and prevent you from spending money quickly and allowing more money for amps, etc. Two, you will need to do these kind of things anyhow to get closer to how your friend's system sounds.
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What was your relatives stereo? If that sound impressed you so much maybe we can come up with a cheaper, but similar sounding, system.
Second the NHT Xd system. Actually had downgraded a great system and no regrets. We're talking from 20K in spending. Okay, here's some things to consider: it's all digital. Xd provides you the amp, subwoofer, two sats and all the speaker cable.

Save a bundle and move your CD collection to a hard drive and connect however best you can. My connection is via an Intel Mac Mini with Sonicwave tosslink glass cable to a Lavry DA-10 to my PS Audio GCP-200 preamp, but I digress.

Shoot, you can use Itunes to control the volume and go without any preamp if you want.

I would consider clean power via PS Audio P300 or better when you can. Used PS Audio P300s can be had for less than $600 and the whole system can be plugged into it. Just upgraded to their Premier Power Plant and that's a whole new level of performance.

Good luck.