First "audiophile" system, now what? Suggestions for best "bang for the buck" upgrade?

Start a new thread regarding the amp and new speakers. List your system and your plan to treat the room.
There are many specifics when matching a tube amp with a set of speakers. A new thread will bring valuable advice.

I believe you have made great purchases on that Vincent amp and the speakers as well. I would be inclined to keep the amp. The question is how your speakers mate with it. This I don't know, however believe it to be what lowrider is alluding to.

I agree (as i posted on another of your threads) that the stylus swap will provide for the greatest upgrade return on investment. 

If room treatment is an option, try some DIY methods. Might want to look up ATC Acoustics, Piper City, Illinois. I have made my own panels with there supplies. 

Lots of experienced advice here.  I don't know where you live, but if you are in a metropolitan area where AC quality is questionable, then a cost-effective power filter/conditioner might make the greatest difference .  In the end, the sound our stereo produce is a direct product of the AC coming to you from your power company.  The more distortion/hash on the incoming AC line, the poorer the performance of your other components.

For the record, it looks to me like you've made sound system decisions so far.  Clean power will allow your entire system to shine!

With your current equipment and if you have good ears you should easily be able to hear differences in cables now. It is not necessary to have ultra-high end gear to hear cabling changes. My systems when I first delved into cables about 30 years ago were by no means high end, and yet in every one cables were obviously noticeable. This is to encourage you that you do not need to put off that decision, if you wish, due to perception that your gear needs to be much higher performance. It is wrong to presume that one needs to have much higher performance gear to hear the effects of cable swapping. 

Thanks for the compliment, I needed that. I put together this system over the last 6 months and the whole proces has been wrought with anxiety and second guessing. I don't have the luxury of a brick and motor store to listen and compare equipment, so all of my ideas came from looking at what was listed on Audiogon, then reading reviews, which then mention other equipment, so maybe something else is good, so read about that, then read a conflicting review, then try to read between the lines. Hours and hours and hours of late night research (I'm guessing most here can relate to), then finally having the guts to make a buy and hoping when it arrives that you get what you thought you were getting. 

I do know that my records and CDs (and FLAC files) sound very, very good. Well mastered vinyl sounds as good or better than digital files on this setup, and it all sounds really, really good and looks cool (which is part of the equation for me). So I'm happy......but what about a better needle?.....then better speakers?.....then better tuntable?...then power supply, then cables, and DAC?... Once its is sounding as good as I've got right now, then the rest will be just more fun. And money.

Thanks for all the good advice.