Be careful, I'm not a HTPC expert anymore but do note that the 6450 you linked to is only 32 bit memory bus. My understanding is that the post processing for deinterlacing and noise reduction is pretty memory intensive and that you should at least go for the 64 bit DDR3 cards. When Anandtech did they 6450 test they used 64 bit DDR5 even so 32 bit DDR3 is pathetic.
I definitely saw that, but given that the 64-bit 6450s run about $40, I was listing that as the closest comparison to the 32-bit 5450 for $10. The 64-bit versions may be better, but they're much more expensive. Still, good to point that out (although I've never read anything saying memory bandwidth affects HTPC functions). This review notes that deinterlacing is handled by the shaders, but perhaps memory bandwidth is still a determing factor in performance:
http://www.anandtech.com/show/2931/4
Now that I'm reading up on it, it looks like you may be right. Therefore, the OP's question would be answered not just by a model number, but also a memory bandwidth. Like HD5450 64-bit, not just HD5450.
Doesn't matter for me - I bought the HD5450 to throw in an old computer just for monitor output.