Oh... yeah I bought the full version. As nice as the included version is it is severely limited especially compared to GR5. Sorry I should have been clear on that but they did give us a massive discount on the upgrade.
However I have been playing around with using TH2's cabinet settings and features to do all sorts of crazy stuff so here's something you might try...
Use GR5 to get a nice sound (but ignore any kind of cabinet/room stuff) then use TH2 further in the chain or on a bus with JUST the a cabinet (as in delete any heads in TH2) then tweak your room/mic/cabinet settings in TH2. That way you get the plethora of amp sounds from GR5 but the slick cab/room/mic features in TH2 (which are severely lacking in GR5 IMO).
As far as ASIO4ALL... yanno I've recently been in a position where I was screwing around without an interface on my laptop and was having a heck of a time no matter what driver mode I was using. I installed ASIO4ALL and things were a LOT better.
Obviously an interface is ideal and that's why people wig out about ASIO4ALL around here because it is NOT a suitable alternative to having a proper interface BUT if you simply do not have one around then it seems like that's a pretty good option to try out.
Also it seems to me they have really done some work on ASIO4ALL since I first encountered it a few years back (or I just was not paying attention back then).
Mind you Sonar brings my laptop to its KNEES so these experiments were using another DAW who shall remain nameless. My lappy is POS though. Yours is likely much more suited to the task.