Omega II Mk1 = OMG, great phone.
With the 313 it sounded dry and lifeless but with the T1S it was very good(a surprise), it is leaps and bonds ahead of any Lambda in many areas, and I didn't find it sounding dark. I wouldn't say it easily worth the hefty extra cost though, at least not with a mediocre amp. And the fit was quite fiddly for me, I had to re-adjust it many times, maybe the Mk2 with the thicker pads would suit me better.