I had M22/VP100/QS8/STF-2, upgraded to M60/VP150, keeping the STF-2. Am now upgrading to VTF-3R. I need a finished sub and the piano black VTF-3 Mk2 has an uncertain ship date. Room size is 20x16. I never had any problems with the STF-2.
Based on my experiences so far, I'd suggest the M60 and STF-2, unless you have a very large room or need a finely finished sub exterior. While the M22/STF-2 was very nice, the M60s are better. IOW I'd prioritize the M60s over a more expensive sub, since the STF-2 is already very capable. But I may modify this recommendation after I get my VTF-3R
That said, if you have a large room, maybe the STF-3 would have more kick. If you want a finely finished sub exterior your options are VTF-3R (now) or VTF-2/3 Mk2 in piano black or rosewood (eventually). But even the "plain" black vinyl subs aren't really bad looking.
But don't over analyze the options. You really can't go wrong with any of the combinations -- they all sound very good.
Much as I like the M22-to-M60 improvement, I heard bigger improvements while on the M22s just by optimizing listening position, speaker angle, speaker calibration level, and source material. So don't sweat the product decision to the exclusion of these items.
E.g. the M22-to-M60 was a nice modest improvement. However going from a poorly mastered stereo CD to a well-mastered Digital Dolby 5.1, DTS 5.1, multichannel SACD or DVD-A is a vast improvement.
With Axiom speakers, a good receiver and sub, you become much more aware of source material quality issues. Bad material is really bad, and good material is really, really good. After getting your Axiom speakers it's like hearing your current collection for the first time.
