I have been playing a lot of sub 10 watt amps for a long time and have come around to favor tweed champ style class A amps. My 50's Gibson GA 5 puts out nearly 9 watts, a lot for a single ended 6v6 amp, but still only comes close to sounding and feeling like a real amp. To put it in perspective Roy Blankenship recently replaced the OT and thought it the best champ style amp he'd ever heard, and built a copy of it for a client. It still doesn't quite overdrive as smoothly as a good class A non single ended amp. So my recommendation is to stick to a tweed deluxe style amp and add a master volume. If you are on the cheap, a traynor bassmate (6v6) version will get you there for about $400 plus what a tech charges for a master volume. Clark and other tweed deluxe clones are not too much more. If you have money to spend, the Divided by 13 CJ11, SJT 10/20 or JRT 9/15 give low wattage joy in the tweed deluxe blackface and GA40 flavors and at least two of these models can have or do have a better than trainwreck style master these days (according to Fred its totally transparent on 10). if you must go single ended, the star NOVA sounds great as does the Groove Tubes soul-o Single. But as these and the cadre of overpriced boutique champ clones (a silverfaced champ will run less than $300 these days and blackfaced a hair more) are being priced in the $1k range, my vote is to go for a better slightly higher wattage amp with a good master volume (or try a variac or hotplate/airbrake/mass attenuator).
I've tried many of the new amps including the Divided By 13 10/20 and 9/15 watt amps and ended up selling them all. I've found happiness in the small 8' speaker vintage amps. Much more character in tone and voice. The modern amps all have better clean sounds but none touches the character of the vintage amps when overdriven. Here's a clip that was posted on the LPF with a bunch of tiny vintage amps. All except the Gibson GA-20 have 8" speakers and 10 watts or less:
univox U45B, about 10 watts with the 6BM8 tube which is similar to an EL84 and half of a 12AX7 in one tube. Gets a great nasty grind when cranked and sounds great sitting at home for low volume jamming. Great tremolo as well.