I need to know what is the difference. I keep hearing that the 4890 is better then a 5770 because of the last 2 number in the card but is that true or not. I need to know so i can buy a card or keep the one that is coming to me now.
No, pay no attention to the numbers. They aren't comparable between different gens. However, I believe the 4890 still is faster that the 5770. The 5770's benefits are DX11, Eyefinity, and lower power (and thus heat) dissipation.
Mainly, 48xx uses DirectX 10 and is on the way out over the next year or so. 5xxx uses DirectX 11 and is the new technology.
The very best of the 4xxx series (4870, 4890) are slightly "faster" than the very lowest end of the 5xxx series (5750, 5770), but nothing to write home about. The 5750 is probably the only one where you'd notice a significant dip. That's pretty much the extent of the overlap.
Also, as mentioned above, the 4870 and 4890 use a lot of power and generate a lot of heat comparatively.
I don't really see much point in buying a 4xxx series card anymore, unless you need a card that's dirt-cheap or uses a tiny amount of wattage (e.g. the 4670) for an older machine.
2. Lower power consumption compared to HD 4xxx series. Example, HD 5850 is more powerful than the HD 4890, and uses less power.
3. True bitstreaming audio for Dolby Digital, DTS, and Dolby Digital TrueHD.
No, try a gaming card first. If you have any issues with it, THEN you can try a workstation card.
Gaming cards in this day and age are perfectly fine for most 3D apps (Maya, Mudbox, and 3Dsmax will all work fine, I assume CAD will also but i haven't used it myself).
Workstation cards used to offer a benefit, and still do to a minuscule extent, but the cost is bleep-ing exorbitant. A 5850 will be as fast as a $2000+ workstation card. And what do you get? Some slightly better drivers (that are released more infrequently). PLUS, workstation cards now come out after gaming cards, so they're all based on older hardware.
Only get a workstation card if the gaming card gives you errors that you can't live with.
People need to stop recommending Workstation cards for common 3D Applications.