beginner seperate system

Schitt  Audio gives a lot of good stuff on a lower budget.
kimber8tc cables,  Emotiva, or Svs for Loudspeakers 
just a sample of low budget entry level gear 

You could get a Prima Luna integrated, used.  I believe Uncle Kevvy has a couple of them listed on his web site.

May I ask why you want separates? With your budget you could get a very nice integrated Amp in either tube or SS. You really are not sacrificing anything these days with integrated amps.   

Jeff, welcome to the rabbit hole of audiophilia! I think a lot is possible in building a system on a budget. You will need to become very familiar with Schiit Audio and their products, because, as stated already, they make great stuff, and great stuff for the money. I own many pieces of Schiit 😀. Also you will need to know the market for other equipment because you will find nice things for less than retail here and on other sites. Through study and knowledge and knowing a deal when you see one, you can build a nice system for less. Also one that is upgradable. Read, study and shop! Good luck! RJ

If you amp/speaker combination satisfies and you want to add tubes to the system then I suggest you purchase a tube amp that is compatible with your amps. I believe most any 2-channel preamp would be superior to usig a AVR as a pre. 

I currently run a Jolida tube preamp into a SS amp. Like you wanted tubes, just not a tube amplifier.  

Good luck in your search!