Sadly the Speedlink clip-on mic has already broken, I've been careful with it but the wire is so thin I don't think it can stand much use. Nothing ventured though at £7. It wasn't an overly elegant solution either with the two wires and you had to ensure it was positioned correctly too or it was muffled and quiet.
I've ordered the PC 360 headset, for a quite reasonable £110. I think my PC 350 is good, but it's very worn, and I want to try out an open headphone, as I've never used one.
So, I'll be able to properly test the PC 360 in my common use environment, to ensure an open headphone is ok, then, assuming I like it (and I probably will), I'll then make a decision on the T70 vs T90. I'm definitely leaning towards the T90, I'd be genuinely shocked if I preferred the T70 sound and general quality. The T90 looks much nicer and has better quality earpads etc as well. The general consensus is that it's a more musical version of the T1. Of course when you break it down the T1 will be better, but definitely not for me, not for over twice as much.
I should be getting the PC 360 today so will perhaps go and test out the Beyer's tomorrow or Friday, I'll have to swap between headset and headphone depending on what I'm doing but that's no big deal. I wonder if there's some sort of desktop amp I can connect to my soundcard (even though it has an amp) that means I could have both connected or something like that... hm.