For the last month I have been using 'Propellerhead - RECORD' software.
Set up to primarily record audio, the software has 3 main screens;
1) A software modeled analog SSL 9000K mixing console (It actually SOUNDS good!!!)
2) Plug-able effect racks (Connect them anyway you want, and includes LINE6 AMP RACK FOR GUITAR, BASS, AND/OR EFFECTS)
3) Sequencer wave window (basically the section where you Start, Stop, and Record)
In the past I've used MIXCRAFT4 and CUBASE LT for desktop recording and both were as I expected.
MIXCRAFT4 -Very nice PC version of garage band, overall sound is as good as whatever you have plugged into it.
CUBASE LT - Sounds a bit better, but you pretty much have to read the manual to get a lot out of it.
Now, using PROPELLERHEAD RECORD - I was really impressed with how my guitar sounded going in 'CLEAN' with the stock 'plate reverb' through the SSL virtual mixing board! (And I didn't even use the built in mixer EQ, Compressors, noise gates, or Line6 amp racks!)
As for the the LINE 6 amp racks I have to say that the STOCK amp models that come with RECORD are fair at best, and it was'nt until I bought the Line6 GX/POD FARM ($100, and some additional model pack, another $100) that I really started to enjoy using the modeled amp sounds! (Basically tweaked the sounds in the seperate POD FARM aplication, then started RECORD and loaded the tweaked sounds into RECORDS line6 amp racks)
I am assuming that you could also combine your Line6 product(s) with RECORD and then use the RECORD software for recording, (You'll have to check it out for your specific line6 product at the Line6 website)
NOTE: You can download a full working version of RECORD and use it to check it out, and you can even save what you record, the only thing you can't do is OPEN UP the saved files, unless you buy the software. (Not a bad deal to try it out)
Bottom line is that RECORD doesn't seem to get in the way of actually recording something quickly, and straight in clean with a little reverb makes it sound great! Impressed enough that I went out and bought it.
I just loaded in a Line6 'Dual Showman' amp w/line6 4x12 cab using one of the RECORD reverb effects and it sounds like I'm playing from heaven.
Oh ya, and I've also recorded my guitar using a real mic and amp, and that sounded great too!
Check it out and good luck!