Hi Jane,
I have heard the 1sc's, and I (personally) like them alot. I'm not sure you will get their full effect when you are working, far away down the long end of the room, but when you are sitting closer in, relaxing, their musicality and imaging should be wonderful. I'm not sure what matches them best - I think they like some power - so if the Classic isn't it, I might consider a Plinius integrated like the 9200 which has power and also beautiful midrange and just good all around. You'll need good solid stands for your Proacs.
I have owned both the Paradisea and the Benchmark DAC, and strongly preferred the Paradisea for its natural sound. I have compared it back to back with my (expensive) Electrocompaniet CD player, with no particular preference, both very good. I definitely like it more than the Benchmark, which I find a bit too detailed and cold. A friend of mine just bought the Benchmark on 30-day trial, I lent him my Paradisea, the rest is history.
One nice thing about buying the Paradisea is that you can use an external CD player for a transport. If you didn't buy the Linn and bought a Plinius integrated, you could buy an inexpensive CD player or DVD player as a transport (e.g. the Oppo which costs $200 and sounds quite good even on its own) and plug its digital out into the Paradisea as well. Both would use this exellent DAC.
Looking at system cost:
Proac 1sc $1200
Plinius $2200
Oppo $ 200
Paradise $ 650
Stands $ 250
Cables $ 250
Laptop $????
Hard Drive $ 130
The total is $4900 plus laptop. Maybe a cheaper integrated (though I'm sure the Plinius would be killer!).
In this system, the only things you'd need to buy used are the speakers, the stands, the integrated and maybe the cables. The CD player and DAC would be new. I think you run little risk by buying the speakers used, and if you choose your seller right, little risk with the amplifier. I do feel bad if I've steered you away from a dealer though - we need relationships with dealers, we need to support them, and people need the support that only dealers can provide. That being said, if you don't feel like you were getting to where you want with your dealers, that speaks for itself. You'll need to decide between working with the dealer and buying online. One option would be to buy the Proac 1sc's and a suitable amp from the dealer.
Best of luck, Peter