To me, the NAD C320BEE defines entry-level. It (and probably the 325) is very good-sounding for the money and you can get one for well under your budget. You can tweak it with better-quality preamp jumpers and antivibration feet from Bright Star or Herbie's Audio Lab.
If you need to spend more, the Linn Majik is a very good amp and very convenient to use. It needs the right speakers since it has less power than the NAD. (It also requires Linn's own speaker connectors.) IIRC the Majik sounds a bit more neutral, the NAD being a smidge on the dry and analytical side like a lot of lower-end solid state. If you prefer (slightly) warm and lush, go for a Rega. If I were using Paradigm Atoms a small Rega would be my choice if I could find one.
At present two of our systems use the 320BEE and Paradigm Titans. The combination works for the kids but I'm not so terribly fond of it myself. My GF has the 320BEE with PSB Alpha Minis and that is a better-sounding setup to my ears; the mids are not recessed in favour of the extremes. (Your Atoms may be more balanced towards the mids than the Titans, though.)
At present, you really can't go wrong with any of these models IMHO. You would be happy if you just jumped on the first that came up from a reliable seller. Study the used prices for a bit so you know how much to pay; you won't lose much on resale if you ever need to upgrade.
Yes, I think tubes can sound better than solid state but IME you will need to spend a bit more to go tubes unless you are into vintage. If I were you I'd wait and do some learning first.
As for your clean sound requirement, you will make any amp, and especially the ones in this thread, sound cleaner with a quality source. That's why I would go for the entry-level NAD; it leaves more bucks for the source.
If you need to spend more, the Linn Majik is a very good amp and very convenient to use. It needs the right speakers since it has less power than the NAD. (It also requires Linn's own speaker connectors.) IIRC the Majik sounds a bit more neutral, the NAD being a smidge on the dry and analytical side like a lot of lower-end solid state. If you prefer (slightly) warm and lush, go for a Rega. If I were using Paradigm Atoms a small Rega would be my choice if I could find one.
At present two of our systems use the 320BEE and Paradigm Titans. The combination works for the kids but I'm not so terribly fond of it myself. My GF has the 320BEE with PSB Alpha Minis and that is a better-sounding setup to my ears; the mids are not recessed in favour of the extremes. (Your Atoms may be more balanced towards the mids than the Titans, though.)
At present, you really can't go wrong with any of these models IMHO. You would be happy if you just jumped on the first that came up from a reliable seller. Study the used prices for a bit so you know how much to pay; you won't lose much on resale if you ever need to upgrade.
Yes, I think tubes can sound better than solid state but IME you will need to spend a bit more to go tubes unless you are into vintage. If I were you I'd wait and do some learning first.
As for your clean sound requirement, you will make any amp, and especially the ones in this thread, sound cleaner with a quality source. That's why I would go for the entry-level NAD; it leaves more bucks for the source.