Then get 5670 instead 5770. The 512MB 5670 is priced at 4.4k and 1GB one will be 4.9k. It will nicely fit within 21k with a few hundreds to spare. You may also look for CX400 with the spare cash.
i5 2400 ~ 8900
DH61WW ~ 3250
Corsair 2GB ~ 1150
Corsair CX400W ~ 2400
MSI 5670 1GB GDDR5 ~ 4900...