parasound 3500 verses parasond jc1

Apart from being differently boxed (as you note) they're NOT supposed to be identical circuits, either. They have a site that talks about that.
As to what differences you'll hear -- in simplistic terms, the JC1 simply sound better in all respects... (IMO)
BTW, why don't you like your present amp?
Cheers

I do ,im wondering if i should buy another 3500 for byamp or the jc1s

Having just read the review of the original 3500 from 5 years ago, they say the bass is its strong suit and the mids and highes are where the improveent should be.(Jan.00)

Which spkrs do you want to biamp? More importantly, does the manufacturer provide for active (or passive line-level) biamping? If so, you'll need a second stereo amp.

A stock 3500 is not in the same league as broken-in stock JC-1's. However, with mods the 3500 is very close to modded JC-1's. Bass control is slightly better with the JC-1's. They are both my personal favorites. The 3500 is actually a very good design and outperforms most amps on the market with mods. For the money, it is hard to beat. See this review:
http://www.audioasylum.com/forums/amp/messages/61129.html

Steve N.
Empirical Audio
Manufacturer