I just got a bit of a break at work to jot down what I remember the various options to be . . .
1. Simplified ($199.99) - stock OPA134 op amp, user can't roll op amps, no front switches (see #3 below).
2. Intermediate ($249.99) - still the 134, but user can roll op amps, no front switches.
3. Top model (299.99) - just like intermediate, except with the four front switches: gain, ety 4p to 4s switch (I'm not an ety guy so I don't know if I expressed this correctly), cross-feed, bass boost.
With versions two and three, you can add the following:
1. For $50, you can add the 627s or 637s. To save money, some have reported success in getting samples from
www.ti.com and installing the op amps themselves.
2. For $40, you can add triple stacked buffers.
These are just my recollections. I don't work for Xin (though given the number of pms I've responded to, I sometimes feel as if I do!), so I'd advise getting in touch with him. In that regard, I get the feeling that he's been extremely busy with the impending release of the SM and so he might not be able to get immediately back to you.
Also, other head-fi'ers, please correct any errors you see in the foregoing.