If you're going to go lower end might I recommend the 6870. On newegg it's cheaper and will probably be about 2x faster than a 7770. (I have one right now, well 2 but I'm waiting for connectors. It's pumping out 414khash/s. Yes I'm mining litecoin and yes most sites say about 350. Don't expect too much more than that I just got lucky I figured out a good arrangement.)

Edit: Forgot the link to the card I got. http://www.newegg.com/Product/Product.aspx?Item=N82E16814202032&IsVirtualParent=1