I have an original Flextone 1x12, a Flextone III XL 2x12, and the usual POD v2. IMHO (and it's just MHO), Line 6 got it right with the original Flextones. I'd have to say the original Flextone and the Flextone II are the best of the lot. The III is great for "oomph", but the sound of the I & II are just a tad better. None of them have that molten, saturated gain like the newer ones, but for a good clean Twin or a chunky Marshall sim, I really think they stand up super well.
To me, the hidden gem in the modeling/hybrid realm is the Peavey Vypyr Tube series. The Vypyr Tube 120 sounds immense, and the Tube 60 is excellent as well. I swapped out the stock speaker with a plain-Jane GT12-75 and it works wonders taking any edge off. The Eminence Delta 12-A is also great for a swap or extension.
Don't get me wrong . . . I love tubes amps, and have quite a few. But for small & medium gigs, the Flextones or Vypyr Tubes really come through. I was laying down a lead for a session a couple of months ago, and brought a Marshall DSL 50 with a 2x12 and the Peavey Vypyr Tube 60 loaded with a GT12-75. We ended up using the stock Bank 1/Patch 4 (Marshall high-gain) from the Peavey with the delay eliminated. Sounded exactly right, and was easy as pie . . .
Suds . . .