Hi Keith,
No you don't need to buy further IR to get a good sounds either, the cabinets just need to be setup correctly (I do use the new Redwirez IR's which are slightly better, but there's not that much difference)!
If you use the the download patch in my link, take the amp drive back to about a setting of 3.
Then select the Blue Bell speakers with an SM57 mic and set it 1" from the cone, then set the speakers Low Cut to 100 Hz and High Cut to 5 KHz. It makes quite a difference using the right frequency cut for the speakers, most Celestion will be fine with those mentioned, but for other speakers look up their operation al range and set the cuts respectively. There are two speakers in path B, they both need to be setup.
For a modern Hank sound set the amp Bass, Treble and Cut to Zero, for the older sounds Bass about 2.5, Treble about 6.5 and Cut tends to be around 6/7.
The patch has routing that that goes to path A, then when it leaves path A it splits to two paths on on B, these are panned left and right for stereo output. Most of the FX on these paths will be duplicated so that they go to left and right channels, but you can alter say speakers on one path to have a different mic which is set further, this is like using two mic's on a conventional amp. In practice you can do many things with this sort of tweaking, some you would find quite difficult or expensive to duplicate with real world gear!
I have a great little boutique amp, but still prefer the convenience and flexibility of the software!
Like everything, it's all easier when you know how!
Regards
Gary
PS: You will probably find it a lot easier with one of the echo units mentioned, its worth looking at some of the echoes discussions on here, particularly those of Dave Robinson!