Need help ! Looking for a low cost integrated tube amp for my office


Looking to upgrade my office system
Music playing through my computer to an Audio engine D1 DAC
At present an old NAD receiver playing to four Vienna acoustics Haydn Grand book shelf speakers and a velodyne sub
Thought I would try my first experience with a tube integrated amp 
Any suggestions ?
fullerco
Yes, a used NAD 356BEE could be found for under $400. Has 2 sets of speaker outputs and an extra set of pre outs. One could set up 4 channels for the 4 Haydns.
If your NAD has “pre in” jacks, I’d get a Schiit Freya+ preamp and get my tube experience that way and upgrade amp later if you want.  Or a used Freya and Vidar would be a nice pairing for not much $.  For an integrated you’re probably best off with a hybrid like a used Rogue Sphinx, Peachtree, etc.  Best of luck.