The Rammstein thing is a Recto and PSA blend as you say. When I use it for guitars I actually prefer it lined instead of using it with a power amp and cab. I've always found a "real" guitar amp to sound superior and no matter how you use the PSA in a real amp/cab combo it's way too muffled and you need to process the hell out of it to gain any definition from it. So I just love it for the thing that it does when lined. Only thing you need to consider, and this is true for bass as well... I find that you generally need to EQ the hell out of it. But the great thing is that it takes lots and lots of EQ very well. So you can basically shape it into anything you want.
I find it very common to need to filter out a lot from 90Hz down plus add a good dose of high-mids (6-9db) and maybe also to filter out some of the extreme high-end. That with a 3-4db cut at 300Hz or something and you're in heaven/hell whichever you fancy.
Here's also a PSA 1.1 / real amp blend thing with the PSA for bass distortion...
http://www.youtube.com/watch?v=h0RK6qsuffU&feature=related