Ketrava,
I have to say, you are probably going to be somewhat disappointed in the HeroLab experience on a $150ish machine.
Primarily because a machine in that price range is very likely to run Android, and Lone Wolf has not yet released an Android version of the program (I am not certain they ever will).
That leaves you with either an iPad (expensive) or a Windows 8 Pro tablet (expensive) or a Windows-7/Vista/XP tablet (oy, see below).
Note that Windows 8 RT is NOT a full operating system, and will NOT run HeroLab, so don't even bother with those. If Lone Wolf isn't going to support Android soon, they would be absolutely nuts to bother with 8 RT.
Now, I have run HeroLab on a netbook with Windows 7, and it worked fairly well, but the screens on those are small, and you can't rejigger the interface of HeroLab to make it work well. The smallest you are likely to enjoy using will be about a 13-14" screen. Anything smaller gets very difficult to work with.
There are some pretty decent tablets out there running Windows 7, but they aren't particularly cheap, probably looking at something like $400 minimum to get one that will handle HeroLab.
The unfortunate truth is that this fantastic program has a pretty high money bar. By going iOS instead of Android, they sort of kicked us iHaters in the teeth. I was fortunate enough to be able to pick up a really nice Windows 8 Pro convertible laptop/tablet (the Lenovo Yoga), but that thing costs $1000. You can maybe get a Microsoft Surface Pro for something like $750 or so, but anything other decent tablet you get is probably going to have to be an Apple product, if you want it to run HeroLab.