I'm in the market for a mid range set of headphones, in particular the Sennheiser HD25-1 II.  I know these are very popular and I would probably be happy if I just bought them, but the availability of replacement parts is concerning me.  I like how the headphones can be completely taken apart...

Basically when I'm at my computer what I'm trying to do is power a pair of over ear headphones something similar to the Audio Technica ATH M-50s, and also power a small 7 Watt mono speaker.  I plan on using the headphones for listening to music, playing games and watching movies, and using the...