Yes I did for that brief test. And today I tried feeding my HP-A8 as the DAC and the WA7 as amp-only mode. This amp actually makes the TH-600 sound closer to the TH-900. With the HP-A8, the difference between the two sounded greater (which to me puts the TH-600 priced accordingly). But with the WA7 amp, I feel it's got great synergy with the TH-600 that it makes that headphone extremely great value for money.
I don't know what MuppetFace was driving her TH-600's with but if it was with an amp that's great synergy (with the headphones), I can see why she said that the TH-600 sound close to the TH-900s.
That sounds great!
Maybe I'll grab a pair of TH-600 sometime... And maybe a WA7 as well. ;)