As an entry level audiophile headphone, I firmly believe the 400S is better than any entry level equivalent from Sennheiser (HD600/650), Audeze (both EL-8 variants) and even the Philips X2. This may be personal preference, but I somehow think you'd find many people who agree.
On the subject of modding, I think it's both the ease of modification, as well as the relatively lower price for these headphones that encourage people to be a bit more adventurous. I'm not sure many would be as eager to mod the HE-1000, for example. I have left mine at stock, simply because I already love it as is.
If you're keen to try out better headphones than the generic dreck out there, I really think you can't go wrong with these as a first "serious" pair of cans. There are much better headphones out there, but I can't easily think of any at the same price range. It'd be a shame to not give this a chance because you think they only sound good modded