I've got a VTL TL 2.5 that might even end up on the market soon -- fully tricked out with NOS Mullards even -- due to the fact that I upgraded to a Rogue 99 Magnum (sure hope it goes fast, if I ever decide to sell it...). What can I say, the Rogue is lots, no holds barred, better than the VTL (but, then, the 99 is also a bit more expensive than the 2.5). Not familiar with the 66, but definitely worth a look as Rogue, and the folks behind it, are top notch. When I got the VTL, the other one I was considering was the CJ mentioned above. If I remember correctly, the CJ was a little warmer and "tubier" than the VTL, but ended up with the VTL due to its expanded feautres compared to the CJ (namely, a remote and a HT bypass loop -- the CJ, with neither, is a really bare-bones unit. May matter to you or not.). Either way, a little patience should turn up either a VTL or a CJ used between $7-800 or so and, at that price, they'd both be a right decent piece of equipment. Well, just looked, and there quite a few of the Rogue 66's available in that range as well. Me, I'd be most tempted by the Rogue -- but that's me (remote, no HT bypass loop -- although Mark O'Brien (aka Rogue Audio) would happily put one in for you for about $150 while, at the same time, politely suggesting that your money would be better spent elsewhere.
As for whether any of this would consitute an upgrade from your current, modded stuff - no clue. A shame you can't find a way to audition some stuff, that's really the only way to know....