Hey guys- hope to bounce this off a couple of people here and see if I'm straight in my logic. I have a good handle on most components, but I'll be first to admit GPU's are not one of my strong suits.
Right now I am running an HTPC build and am trying to cut the excess noise down. I have an Asus HD 6670 from an old system running right now, along with an Athlon X3 455. I'm thinking about picking up an HD 6450 with passive cooling, and perhaps even down to a 65w Athlon X2- although that's neither here nor there I suppose. The mobo is an M5A88-M, just for reference.
My question is whether or not there is ANY perceivable gain from having the current, more powerful graphics card in place if the system is only used to browse the web, stream video to a 32" 720p television, and play 720p bluray/television rips? There isn't a single game installed, nor will there be (okay, maybe Peggle)- but I don't want to hinder the system at all without knowing.
Based on reading about movie / video playback capabilities of the older Radeon HD 4xxx and 5xxx series, lower end cards like the HD 6450 will lack some algorithms that affects the display quality. The difference is relatively small and you can only tell the difference if you were to scrutinize the displayed videos side-by-side between a Radeon HD 6450 and Radeon HD 6670.
Starting with the mid range cards, all Radeon HD graphic cards will have the same video algorithms. Meaning all Radeon HD x670 (like HD 6670 and HD 6870) cards and above produce the same video playback quality
The 6450 should work fine for your needs. I don't have a htpc,but I have a slimline Dell with a 6450 that I use for the same uses as your htpc. I find bandwidth from the cable more of a limit than the gpu.