That is a great card for a great price. My uncle has a 9550 (mind ya, not liking shopping online, he payed almost 4x the price)
Most of the 9550's are great great overclockers, easily getting a 1\3rd overclock.
It will be able to play hl2 at 1024 x whatever pretty easily. However, if your CPU is under 1ghz, your in trouble. On a 9200SE running with 800 x 600 and eye candy off, i got CPU limited in HL2 from a 1.7ghz p4.