I play my Heritage H535 through a '71 Fender, Princeton with a Bogner, Metropolis 1x12" cabinet under it. The combination of the 10" and 12" speakers together works well for me. My ultimate amp with an ES-335 style guitar is a tweed Fender, Bandmaster or a good clone of that amp. The tweed...
The early Legacy's have Seymour Duncan SSL pickups. Somewhere around 1995 G&L quit using the Duncan pickups and started building their own pickups for the Legacy and Fullerton models. I prefer the early models too. I have a '93 Legacy.
I bought my Collings 001mhsb used and it's been problem free! In my opinion, used is the only way to buy a guitar. With used guitars the original owner takes the initial hit in depreciation and the guitar will be a bit broken in.
Congratulations on your new Collings! I play an '08 Collings 001mhsb and I use Ernie Ball, Earthwood 11-52 strings. I know they're a bit light for a short scale acoustic but they work for me. As others have stated, strings are cheap and don't be afraid to experiment.