I have a Radeon HD2600XT GDDR4 overclocked to 850 core/1170 memory (2340 DDR). I have never seen this card hit over 65 C. This is on a Crossfire 480X motherboard with an AMD Athlon X2 3800+ running at 2.56 ghz and 2 GB of memory running at 426 mhz (852 DDR). The video card is currently running at x16 bandwidth due to the fact that only one graphics card is installed. I score roughly 11,000 in 3dmark05 and get an average of 400 fps in ATItool 3d view. I also get constant 20-40 fps in Crysis on medium settings at 1024x768.

My questions...

1. Would adding another 2600XT GDDR4 be worth the money?

2. Would I see a large jump in performance?

3. Would the slower x8 lanes slow things down noticeably over an x16 system (would a 580x or 3200 chipset be worth upgrading to)?

Just sell the current card and get a single HD3870. More than worth it.

1. not really
The bottom line is, a single Radeon 3850 would beat the snot out of two 2600 XT's
You're better off selling your 2600 and buying a single 3850.

2. no. Noticable in some things, but not a 100% jump. More like a 10 to 50% jump.

3. no. The PCIe bandwidth is not really a bottleneck

would a 512-bit 2900 PRO do the trick?

yea, but they dont sell the 512bit pros anymore the last ones left are the 256bit ones, and the 2900GT's

rather i agree with them get a HD 3870 you will see HUGE increase in performance, compared to your 2600XT

^Agreed. or a 8800GT 512MB

I am on the tightest budget you can imagine though...

You guys have any experience selling cards?

Where is the best place to get rid of one?

I usually just go ebay.

Might get mote money if you put it up in the local buy & sell.

The 2900Pro 256-bit card is still a great deal. The 256-bit bus doesn't seem to affect performance at all. Just keep in mind that the 3870/3850 and the 8800GT/GTS G92 use a 256-bit bus. It is extremely overclockable. I have mine at 850/1000 and I get 11k in 3Dmark06. It's a little loud but for the performance and price you can't beat it.

I run Crysis with it using the DX9 Very High mod and I get about 30FPS @1280x720. I highly recommend this card to anyone that doesn't have a $10 dollar PSU. The power requirements aren't as high as the old Pro or XT because it only needs one 6-pin or 8-pin adapter to run it. They are going on Newegg for $159 right now, I was lucky and picked mine up for $130.