I also have the Signatures and I am using both the Raysonic 128 and the Wadia 302 as sources I have been quite happy with both a Cayin A100T and a Paragon Three/Five pre-amp/amp combo. Both are very responsive to tube changes. I've only had the Cayin for 3 or 4 months but it has been trouble free. It is well built and operates very well with its remote. It also has both Triode and UL on the fly, although IMHO the Triode mode is a little soft and fuzzy in the upper mids - not a draw back if you like your music laid back though, and the amp runs much cooler so I assume you'd have very long tube life. I put mine in triode for casual/background music. It costs a bit more than you mention but sooner or later they will come up for sale.
I think you might find the 3/5 combo in your budget, and it is also a fine set. Down side is no remote and it is only UL, no triode option. But it runs cool. I've had this combo for 2 1/2 years with out problems. FWIW.
I think you might find the 3/5 combo in your budget, and it is also a fine set. Down side is no remote and it is only UL, no triode option. But it runs cool. I've had this combo for 2 1/2 years with out problems. FWIW.