I know that Decware amps come with a 30 day satisfaction gaurantee as long as no special modificatinos are requested (such as custom colors and/or exotic woods). That should put you at ease with trying one of their tube amps and/or other products.
If you're interested in SETs I would recommend either the (a) 2 watt Super Zen, (b) 2 watt Zen Select, or (c) 6 watt SE34i.3 (aka Rachel). If you need more power I would recommend their 25 watt Torii as even though it's a Push/Pull ~ it retains a lot of the SET flavor of even order harmonics by the way its designed. I believe most amps in the Decware lineup are designed to mimick the positive aspects of SET amps. For instance I have a Decware Taboo Mk II (6 watts) that is a SEP by design, but it retains a lot of the SET flavor in the midrange, but on top of that it has some serious balls in the bass department ... to me it's the best of both worlds.