This....
If what you want is a clean pedal platform to let your pedals shine then unless you're really playing low volume, you're going to need some headroom. Meaning, probably at least 12-15 watts or in the "Fender Blackface Princeton" range. (That would be an excellent choice btw).
25 watts is probably better. This part of the reason I've moved mostly to the digital modeling domain. My wife has a condition where she can be hypersensitive to loud noises and even from across the other side of the house me cranking out riffs to "Custard Pie" on my tube amp just isn't going to fly anymore.
The UAD Apollo system is simply astounding at how close it can sound and feel like a real amp. In my "MOST HUMBLE OPINION" heads and shoulders above anything else out there in the digital modeling world for studio applications (E.g., Nueral, Helix, Kemper). But even then, only certain amp models, there's some real dogs in their line up too. (I hate the Plexi model, and the 55 Tweed model) But 99% of the time I use the Fuchs Overdrive Supreme model, clean channel, which is just a great clean pedal platform.
Having said all that, here's a real unintuitive suggestion I'm going to make. There was recently a thread about Dumble amps (and a lot of dumping on them). The one thing I really like about "Dumble-style" amps is not the super saturated gain channel but rather the big bold fat clean sounds you can get. Makes sense since the original amp D made was a modified Bassman head for Robben Ford.
Most of the Dumble clones out there are stupid expensive but there is one really really cool amp that I've been eyeing.
The VHT-D-Fifty.
It's a point to point hand wired clone of a Dumble-esque circuit. But I'm mainly interested in it as a clean pedal platform. Basically a dual 6L6 50 watt amp. I'd probably never use the gain side, but just the clean channel. The heads can be had for around $900, which is pretty ridiculous for PTP hand wired amp. (Note that it doesn't solve MY particular volume issue hahaha.)
Another unintuitive suggestion I'm going to make, is the Mesa Boogie Mark 5:25. I sold mine because I only ever used the clean channel. Oh but WHAT a clean channel. Like most Boogie amps, it's "option overkill", too many damn knobs, and toggles, pull this push that, which I really tired of. But the clean channel is the same circuit as the Boogie Lonestar, which is one of the best clean tones ever, especially the 6L6 version. awesome pedal platform. I really regret selling it, but they can be had used for a reasonable price.
This is the amp I currently use,
Revv D20. It was designed to be an extremely neutral sounding clean pedal platform with a built in Torpedo Cab IR/Reactive Load/Digital interface. It's actually quite a killer sounding little 20 watt amp out of the box and can be further dialed in with some better tubes. My problem with it (aside from just being a fickle gear slut) is that it's a little TOO neutral sounding. I can dial in some Blackface Deluxe type sounds or some Bassman clean sounds but it never really quite gets there.
I think maybe if we work backwards on your question, starting with what your budget is, it would help narrow down what you're looking for. There are LOTS of choices out there these days at every price range.
Edit: Dang, late to the party as always....Congrats on the Blues Junior snag! There's a huge rabbit hole you can fall into with that amp, lots of useful mods available for it, dedicated forums, etc.
