No, I don't think the 24" will be too big. I was just concerned you'd try to do a lot of gaming on it and with the native res being 1920x1200, that can be pretty tough on systems.
The HDR 45s work well with my PCs but there are a couple of things I don't like about them. They're a little uncomfortable for extended sessions and the battery life is basically what it advertises. Reach the limit and they go off. I have some AR wireless headphones that I use with my home theater system and they far surpass their advertised battery life. They're also a lot more comfortable for extended periods of time but the Sennheisers have a much, much cleaner sound (the bass is very tight). The Senns also automatically tune really quickly. The ARs only take around 30 seconds (sometimes, sometimes they tune faster) but when waiting, that 30 seconds seems to take forever.
The HDR 45s take a second. The ARs do better further away from the base but when close to the base, the HDR 45s are probably a little better (talking about any static or interference that might occur). Those are the only two brands I've used so far.