ATI hybrid crossfireX

I'm thinking about getting a new board. Found one pretty decently price, it has onboard graphics.

Video Chipset ATi Radeon HD4200 Graphics
Chipset ATi Multi-GPU Support Hybrid CrossFireX

I know I want a new GPU, but since the board only offer one slot and it offers Hybrid CrossFireX, which are the GPU's that work best for that? Do you have to stay in the same family? Obviously ATi, but I mean:

In the 4200 series?? Or can you pick any GPU like 4800 series or even newer 5000 series?

Do you disable the onboard graphics before you install new GPU?

TIA

Unless you are on a very limited budget with regards to a video card, then it isn't worth getting a card to run that way. Pretty much anything from the HD 4670 and up will be faster than any of the cards that are compatible with Hybrid CrossfireX (which unless things have changes much with the 8xx series chipset, is limited to HD 2400 and HD 3400 series cards),

ATI CrossFireX™ | GAME.AMD.COM

Edit: Just looked up one of the new Gigabyte 880G boards,

GA-880GMA-UD2H (rev. 2.1) - GIGABYTE

and it looks like with the 880G it will also work with the 5450 in addition to the 2400/3400 cards.

The one nice thing about using an ATI card with the AMD boards that do support Hybrid Crossfire is that when used with a higher end card makes using up to four monitors a breeze; enable both the onboard video and the Surround View option in the bios, and you can run up to 2 monitors on both the card and the onboard (which works very well by the way).

WOW, looks like its not a good feature at all. So my choice will be to the a good single GPU $100-$150 range and disable the onboard graphics once I get the GPU.

I'm don't think I need CROSSFIRE as long as I get one good card. It still will be a major improvement from a 8600GT which I currently use.