The 9550 is a downclocked 9600 if you have a 128-bit card. If you benchmarks are decent you can be assured that your card is indeed 128-bit.
As far as DX9 cards, you should have listened to some of the people here or asked first.
If you gonna do the DX9 thing and expect decent framerates at above 800 x 600, you need a Radeon 9700 non-Pro or better, or for nVidia a 5700 Ultra or better. Yes, some of the other cards like a 9600 Pro or 9500Pro can do OK, but they use the DX9 rendering and the latest gaming titles put the hurt on them.
If you are absolutely budget limited, a good overclocking 128MB Ti4200 will beat these lessor DX9 cards without AF or AA because it won't even try DX9. Yeah, it won't look as good, but we said budget and it least it can play them reasonably smoothly.
Recently I picked up two Ti4600's for under $70 shipped, just to rock Unreal 2003 online. Using OpenGL rendering at 1280 x 1024 I get about a 70fps average with a ton of players, that's what budget is all about.
Getting back to your 9550, the core should overclock nicely. Use RageTweaker and check the memory chips.
They're probably gonna be 3.6ns or higher, so don't expect anything over 600MHz max (if you're extremely lucky), and you probably won't get that.
I would go back to the Omega Cat 3.10's, they seem to be the fastest for gaming unless you're having driver issues in newer games.