HD3S - your thoughts please!

[Lyndon Johnson]

A change in home-life circumstances means I am now needing to take refuge in the spare bedroom and listen through headphones. Currently I use an old pair of Sennheiser HD560 Ovation plugged into a Marantz CD6003 headphone socket. It's okay but I am considering breaking open the piggy-bank for an upgrade.

My thinking is a nice headphone amp first, then to take that along to a good dealer and audition some 'phones in the £400-£800 range.
I am keen to build a HD3S and feel confident with this, having built a K5881, KLP1 and KLPP2 in the past.

I have some questions that you may be able to help me with....

1) £560+ is quite a lot of money - does anyone have any experience of HD3S compared with similarly priced built units sound-quality wise?
2) I can't find any information on the website on what components are upgraded with the 'plus' model and what effect they have on the sound quality. Can anyone help me on this ?

Many thanks!
Lyndon