I bought the SR-507 new and IMO it's a big pile of turds. Its sound signature -- as spritzer has mentioned many times before and I really should have listened -- is that of an extreme "U", and its soundstage is so shallow it's like an electrostatic Grado.
Boo urns!
As you said, the drivers aren't meant to last for more than 20 years -- and most R10s are pre-2000. The risk is not insignificant since finding matching replacement drivers are almost impossible (and afaik I've only heard of one HF'er, Purk, who has owned a spare driver).
Ehh, I told you this on AIM, but I thought I might repeat it here for other people who might have fit issues:
You can bend the shit out of the OII's headband for a perfect fit. I bent mine out the other day, and it fits my head perfectly now (when it's on the banana rack, the two earpads don't touch each other anymore!). Perhaps the owner of the OIIs you tried had a big head,
You'd still have to get a proper transport and DAC that can sync together, and who knows how the Transporter performs as a $1700 DAC..
The only ~$1700 DAC that pops up to mind is the Stello -- there's doesn't seem to be too much in that category. In the $2500 category is the LessLoss, but you gotta get your transport modified or upgraded for that.. something like an RME Hammerfall doesn't come cheap!