Newbie building modest system ...what amp?

I have a adcom gtp 400, rega rp1 so far with kimber kables for interconnects and speaker cables.

In search of Vandersteen 2ce's.

Looking to spend in the 500-600 range used for a power amp. Then will be on the hunt for a used preamp after that.

Any input would be appreciated.
Any old Rega, Arcam, or Linn, will do just fine. Dump the adcom as soon ad you can, you won't believe the difference.
Sell the GTP-400, add it to your other money and buy a decent integrated amp. The Adcom pre is a POS, I know as I owned one.
I've owned 2ce's, 2ce Signatures and 3a Signatures. I'd look for a McCormack DNA .5 Absolutely perfect match for Vandersteens. You may be able to find a DNA 1.0 in your price range and it does have more power, but I've always found the DNA .5 to be slightly smoother in the treble.
A used Belles 150A Hot Rod amp with a tube preamp into Vandersteens is a classic combination.
+1 on the Belles 150A Hot Rod. One of my favorite all time amplifiers. Great match with the Vandies.
McCormack is a great chice with Vandies. However, I too suggest you sell the adcom and get an integrated, or if you can swing it, separates, but IMO the adcom will be the weak link. You dont want your pre amp to be the weak link.
i recently had three amps around this price range in my system at the same time - mccormack ht1 and 0.5 both smc modified and a macintosh mc7100. all were very good and exceeded my expectations, but the macintosh was definitely the best of the bunch. it’s an excellent sounding amp, and for the prices they sell for used (generally around $900), it’s an absolute steal.
The old McCormacks are great in that price range. I would suggest you consider a good passive volume control, like a Promitheus REF 4 to go with the McCormacks. The unmodified McCormacks have a very high input impedence and play well even with resistor based passives. No issues at all with a transformer volume control like the Promethius. For 1100-1200 I think that combo will get you more than any integrated I know of in that price range. I believe McCormacks also are nice with Vandies.
I have had McCormack DNA125, Forte 4A and Classe 100. Personally I liked the Classe best. A HiFi tuning fuse in the Classe made for a nice upgrade.
I recommend too going the integrated amp route as the best way to maximize your budget.

There is a Denon PMA A100 integrated list on Audiogon now, and I recommend it. It is the anniversary edition of the PMA, which I used to own. The regular PMA was a a very good piece, and I believe the anniversary version had upgraded parts. It has a very good phono stage too. It's also very high current, capable of 20 amps continuous, and 125 amps peak. I sold mine only because I was going from having two systems to one, and that final system costing about twice as much as the other two combined. I simply wanted to free up the funds. One last comment. About the original PMA, on its website, The Absolute Sound said, "At its price point, nothing else comes close."
Think I'm going to take a different direction....

Preamp is going to be first, then vandersteens and finally amp.

So more research to do ....
There is more than one way to skin a cat. I've heard some incredible systems that were built around the amplifier (SET) and not the speaker.
While I'm sure the majority of the people still start with the speakers and work backwards, there are other options that do work well too.
Hello Mswobo, Do you have a old receiver or something to listen to music with while you work at your system? Old speakers? If you have a receiver then buy speakers. if you have some old speakers get the amp first.

If you have nothing now it will not matter if you start with speaker (Vandersteen's), or an amp. You will need both to make music. Most people match their amp and speakers, and then add the preamp to their taste. At your price range IMHO, the preamp is the hard part, although I have seen some small Tube preamps with limited inputs lately come thru Audiogon. (Decware). If you do go this route, separates, check back here regarding impedance of the components and I am sure you will get help in that area.

I think choosing a classic speaker like the 2ce is very smart. I also think Tpreaves is right about the integrated. Although they don't have a phono, maybe the Bel Canto 300i or Evo2, or an NAD.

Good Luck!
i have a rega rp1 keeping

amp...adcom 545
preamp ...adcom 400
speakers...DCM TF600's

Those 3 I want to upgrade one at a time over the next few months.

A audiophile friend recommended I up grade the preamp and not the amp for now so I can spend more on a preamp.

The Vandersteens always seem to be available for sale a lot so thats why the preamp then the speakers was my thought process.
The speaker to room/listening position is the most important consideration, followed by the speaker to amp consideration, followed by the amp to pre consideration. Take those considerations out of order at your own peril. It might work, or you might box yourself out of better options.
For the budget of $600, Baby Amplifier from Sophia Electric could be the best choice for sonic performance and resale value. Noted the increasing resale value due to rising cost of making them in the first place.