Is it worth setting up Crossfire?

I have ordered a new motherboard with ATI 4200 graphics processor onboard (yes it's a few generations behind I know). It says it is Crossfire ready and from reading I've done this means supporting another graphics card of similar specs for faster gaming.

I'm not a gamer but am a fairly heavy user of Photoshop CS4. Would I see any improvement in 2D rendering in PS? I suspect the extra memory on the added card must give some advantage eg less use of RAM.

The series 4000 cards are pretty cheap now - what would you suggest?

My two cents, I don't think it wouldn't be worth it (for CrossFire)--however, I don't really know how CrossFire affects GPGPU. And, looking at what you're doing, I'd suggest going with the 5000 series cards over the 4000--I don't know of specific numbers comparing the two generations of cards, but ATi has put more emphasis in GPGPU processing in the 5000 series cards.

GPU and OpenGL Support in Photoshop CS5 and CS4

Thanks - the onboard GPU should run CS4 OK with OpenGL 2.1. Can always add a card later.