Vminnovations are selling Senn 428's for 27.99 W/free ship on their ebay page. Shipping is U.S only tho:
With the Sennheiser HD-428s, the bass mod makes them sound better than the famed HD-580 in my opinion. The weak spot though is the plastic headband that does not grip as good as I would like. But I am working on a mod/fix for that. The stated price is crazy good for these headphones. I think a modded pair might just make an owner of the HD-600 cry.