what impacts the sound quality more amp or pre-amp

The Alon II speakers are specified as 87 db efficient and are, I think, 4 ohm nominal impedance. This is a difficult load for most tube amplifiers to drive.

My personal feeling is that if you want tube sound that you should go with a tube amplifier. I think this makes the most difference. But it implies certain speaker choices too.

From a practical point of view, it is going to be challenging to find a tube amplifier for $500 - $800 which will be able to reasonably drive your speakers.

In the context of your system and with your budget, my feeling is that a tube preamp would be your best bet.

The Mapletree Audio Line 2A SE preamp is $760 new. It will likely survive many system changes and upgrades that may or may not be in your future.

I'm happy to stand corrected. Generally, I've been choosing efficient and easy to drive speakers to pair up with comparatively low power tube amplifiers. It didn't occur to me that Harbeths, for example, are relatively inefficient but remain easy to drive.

I realized that the numbers I was giving for efficiency and impedance were actually for the Alon IV. Having said that, I can't find Alon II measurements and specs. However, I did find this thread:

http://forum.audiogon.com/cgi-bin/fr.pl?fcabl&1011043701

Where at least one person says these should be tube friendly.

Personally, I'd go with a tube integrated amp, or a tube power amp with a passive preamp. You still need to pick the right amplifier of course to get the sound you want as not all tube amps sound the same and there can be striking differences between them.