Okay, where to start?
 
I'm basically building a new PC and upgrading my current HTPC.
 
1. The guts of my current PC (see specs in sig) will be going into my HTPC. I'm not concerned with Blu-Ray or HD DVDs at the moment.
2. My new PC will be built around a Q9450.
 
My current GPU is a Radeon X1900XT (512MB). I am contemplating the following things:
 
1. Keep my X1900XT in my primary PC and buy a quiet 8600GTS (Asus' silent solution comes to mind) for my HTPC.
2. Place my X1900XT in the HTPC and buy a 8800GS for my primary PC to hold me over until nVidia releases a new GPU generation (after 9xxx).
3. Place my X1900XT in the HTPC and buy a 8800GTS (G92).
 
I'm not really a hardcore gamer anymore, but I play a mix of games like turn based strategy (Galactic Civ 2), some FPS, and simluatiuons (X3: Reunion, Silent Hunter 4).  
 
Cost isn't too much of a concern (unless it's over $300), but with the exception of the video card, total spend is about $2,100 on parts already purchased and the few yet to be ordered.
 
Obviously I don't really wanna spend money on a uber card if I'm not really gonna take advantage of it very often.

For the HTPC, it all depends on what mobo you have. Going Intel, Ill assume you have no HD capability, so youd want a card thatll do that for you, like the 8600GTS. As for your main rig, Id wait, as all the cards currently out will be reduced in price in a month or two. By then youll see if you want to keep the 1900, or take advantage of a cooler, better performing card at a decent price

The 9600GT and 3870 are very cheap at around $150 on newegg. Both are great cards for pretty much the same performance.

As stated, the parts that will be making up my HTPC is in my signature:
 
E6600 @ 3GHz |
Corsair XMS 2GB DDR 667
MSI 975X Platinum v2  
Audigy 2
Seasonic S12 500
 
As stated, I am not concerned with an HD player at the moment so the X1900XT can suffice for now.
 
As stated, most of the parts for my new rig has been purchased. The parts yet to be ordered are as follows:
 
1. Case
2. Case Fans
3. Sound Card
4. RAID Card
5. Video Card

 
Kinda like the half way point between the 8600GTS/8800GS and a 8800GTS. If I go halfway, I might as well go all the way for the 8800GTS.
 
The 9800GTX kinda starts at my max limit of $300.