I know its not ideal combination but I'm tempted to buy this tube amp with 600 ohm output. Mainly because it's a great deal for 150 bucks and it uses all premium parts. Just how bad the sound quality will be affected by using 600 ohm amp to drive 300 ohm headphones?   According to Bruce Heran...

I took apart my 10 yr old HD 280s today to mod it and I was surprised to see that the driver it uses is the same as HD555/595. Or may be I think the plastic membrane part is the same as HD555/595 but with 64 ohm magnet.   Also the driver seems to be damaged it sounds fine though.    I wonder...

I've been using Sennheiser HD280's since 5 yrs or so. I'm looking for an upgrade but I don't want to spend more than $150(I'm on a student's budget). Has to be closed design. I see Audio Technica ATH M50 going for around $125 these days. Are they a considerable upgrade over HD 280 or pretty much...