haha thanks!
i'm kind of new to this
also i have one more question:
does the AMD HD7990 GDDR5-6GB
Dual GPU DVI/4xMini DP Graphics
Card GV-R799D5-6GD-B really runs at 1250khash/s (1.25mhash/s .-. )

?
(
https://litecoin.info/Mining_hardware_comparison)
The most H/s per $$ right now are your R9 270X (cost around $200-250 and get around 460+ KH/s each), but you'd have to build quite a few rigs if you want to go big.
The Sapphires seem to crank out the most Hashes and run cooler compare to the competition. But all brands are fairly good.
The Asus in the 270X seems to have problems when overclocked from what is posted online.
The next best KH per $$ are your R9 280X's (cost around $420-460 and give you about 750+ KH/s each).
I went for the the ASUS R9 280X TOP's because they were said to be the most silent and had great OC room and I really like them ... I'm getting 780 KH/s per card even at -10% power.
Again, the Sapphire R9 280X Vapor's and Toxic's are said to have the best KH rates but the fans were stated as noisier when reviewed.
To wrap up ...
So if you want to save space and have quiet rigs, I'd say the ASUS R9 280X's (780+ KH/s each)
If you don't care about noise, but still want to save space, then the Sapphire R9 280X's (800+ KH/s each).
But best bang for buck would be the Sapphire R9 270X's (480+ KH/s each), but you may have to build many rigs to go big.
If you have lots of $$ and very little space then the beast of a card you mentioned will crank out the most KH/s for sure.
Hope this helps.