-IMHO-
I'll add a few more things to be filled in by some of the other regular folks here who have more cards in their deck than I do.( mylife: Sometimes I feel like I'm playing solitare with a deck with all the aces missing)
Avoid Retail Prices: A couple have said you need to buy retail if you listen/audition in a retail store. I would buy used equipment I haven't heard based on sound advise before I paid full retail price for anything (I'm not only clueless but cheap too!). I admire the ethics here but you will take a huge hit if you pay retail prices. I don't think it's possible to put together a really nice music system for 5k paying retail. In fact, I just saw a system advertised for 11.9k retail in the local paper that is a complete dog - multi channel dog. .
Home Theater or Music: Not mentioned above at all. You note that you are into "HI-FI". Music or home theater? Just my opinion but the industry is really pushing HT. At your price point (I think at almost any price point) Stereo two channel is the way to go. If you spread your $$ out to six speakers and then ask the amp to handle all of that you are giving up A LOT of quality when it comes to listening to music. Buy a two channel system.
Law of diminishing returns (general rules are made to be broken): Not going to break down component by component but I think (without going into vinyl) you are approaching the point where return on the dollar starts to diminish very quickly. You get a really nice bang for the buck system in the 5-7k range if you buy smart. Also, with regard to components remember: general rules are made to be broken. If someone says that generally returns start to fall off at 1500 for solid state amps and you have a great deal infront of you for 700, well take it. Sometimes the industry puts out a winner (the little NAD 370 -there are others too!) at a lower price. Take advantage of it. General rules about what you have to pay for good stuff are broken everyday by folks here at audiogon and elsewhere.
The old " It's Your ears argument": Out of respect (lots of kind folks here) lots of folks will tell you to listen, listen, listen. The pitfall is that if you are new to high end, your ears might not be all that good at first and may change in time. I know mine have improved (or at least changed) with listening. I really remember (some years ago) running from venue to venue trying to distinguish the speaker I heard at store X, run with ABC equipment in a 14x 31 room, to what I heard at Store C, run on EFG equipment, in a 14 x 14 room. Not really productive. That's why some have said bring the speakers home. This is also hard to do logistically and it is very hard to make close calls when you listen to speakers hours and days and usually weeks apart. For most of us it involves some listening, an educated guess, and then a leap of faith.
Speakers: Buy the best you can get!!! Speakers have a huge job to do: Electrical energy is transformed to magnetic energy which is transformed to mechanical energy which is transformed to acoustic energy. There isn't this much going on anywhere else in the system. Some folks have suggested spending as little as $1,500 on speakers and IMHO that is sonic suicide. Unles you get some really exceptional deal/value out of proportion to what you spend.
I like Northcreek. Go to Northcreek.com and look at Rhythm kits just for the fun of it. Reading the site will give you a little education about issues in speakers anyway. A last pitch. They have externally mounted crossovers (along with the handmatching of the drivers to within .5db something almost nobody else does and certainly nobody at this price). This means you can fine tune the speaker, especially the tweeter w/o having to tear the speaker apart - just open the crossover compartment on the back of the speaker and add a resistor to the tweeter's signal path. You can add in .5db steps. What a Country! It is also very easy to add a sub later if you are a bass freek.
Avoid stupid Mistakes. You can probably do this simply by following the conversation here at Audiogon on different points and paying attention to what brands get good reviews over a few weeks. No state secrets here.
Matching Components: Books are written about technical aspects of each component and I am not smart enough to write one and you probably do not want to spend the time to become an electrical engineer before you buy. A couple obvious and common mistakes to avoid. I'll let some other folks give others as this is already way to long.
1)Buy a speaker that presents a fairly constant load to the amp. This makes the amp's job lots easier. The speaker is an inductor and acts like a resistor in the circuit (big over simplification but hey). The nominal impedence that is listed on most speakers is very misleading. Impedence always varies with frequency (and other things)and sometimes the manufactureer gives rather dubious figures. Make sure the load is good through the entire frequency 20-20kHz. This makes Amp's job easier. Well designed speakers do this. 2) Try to buy a fairly effecient speaker. One recent post inquired about buying an amp for a Paradigm 100 which was rated by Paradigm as about 90db (trying to remember here). An astute poster noted that Paradigm's measurements were off and that it really performed in the low 80s according to independant testing. Big difference in what you want from an amp - need more power to make them sing! The N Creek speaker is a true 90.5 (over 90 is considered quite effecient) and presents about as constant a load as you find. You will not need a huge expensive muscle bound amp to make them get up and go.
3) Amp: Watts is not where it's at. If it were every K-Mart amplifier would be a winner. Again these can change with frequency (and other things). Look for "continuous" watts or RMS(Root Mean Square) when you inquire about the amps power and remember "power" is two separate things (at least). If you know anything about electricity you know the "Pie" rule. Amp's power is 2 sided (at least) Power=current(I) times Voltage(e). Make sure your speaker can deliver some current when the time arises.( See one above - Impedence (in Ohms) will fall at some frequencies (lower) and the amp has to be able step up to the job.)
If you get a speaker that is fairly effecient and presents a fairly constant load and an amp that can push a little current you will have a nice match generally, or at least you have avoided a couple common mistakes.
I'll let someone else tell you why you want class A operation because my insomnia is no longer keeping me awake.
Good luck and let us know what you buy will you !