Thanks. So far among all PC programs I tried I like Sony ACID Pro the most, despite having a few gripes about it, like almost all VST plugins settings being reset everytime I close the program, even after saving my work many times. Because of that I have to keep ACID Pro open until I am certain my song is done and no longer needs adjusting. It's not too much of a problem right now since I leave my PC on 24/7 and if I expect to remix a song in the future I can just export certain channels separately from the others then reimport the wav files later in the program when it's time to remix.
I got the trial version with full functionality right now. Afterward I'm gonna give Sony ACID Music Studio trial a shot. If it isn't that bad and I can get used to the inline midi track editor I will buy this one, else I will wait a bit for Acid Pro. I would prefer to buy it so I get the package and am certain my serial number will work forever and that I won't end up with malware from torrents or illegal downloads.
Besides Sony ACID Pro so far I tried other PC softwares:
Ejay Virtual Music Studio (which is Dance Ejay, Techno Ejay, Rave Ejay and Hip Hop Ejay bundled together): I didn't liked it. First, for a grid-based sequencer like Ejay or MTVMG I prefer using a gamepad than a mouse+keyboard. Secondly, it didn't seemed to have as much options in the riff/melody editor compared to MTV Music Generator and it seemed more limited, and third, I hated the way the beatbox worked. You can do nice stuff on it (I checked on Youtube) but I just didn't felt comfortable with it.
The PC version of MTV Music Generator: As with Ejay, I don't like having to use a mouse and keyboard in a grid-based sequencer. I prefer controller. Controls are even worse than Ejay too. It has more effects and filters than Ejay Music Studio, but their sound quality is bad compared to the Playstation version. On top of that it crashes all the time, even on Windows 2000 and ME, even thought the software is supposed to be compatible with them. IMHO, despite the limited 2 MB RAM for samples and having to connect wires to your PC to record your songs or use an emulator, I prefer the PS1 version to work with. I can do a song in 3 hours in it and on the PC it takes me 12 hours to make the same song.
Music 2002 Club Edition: It's the same software than MTVMGPC, but with samples from Digital Hitz Factory for the PS2 added to it. It also crashes a bit less often. However I got the same other problems with it.
FL Studio: I just can't get anything done in it and can't get used to it. The interface is also very cluttered. I prefer something simple like MTVMG interface.
Magix Music Maker 14: I haven't tried the older versions of Magix but I tried version 14/2008. It took me less time to get used to it than Sony ACID pro and the interface is almost the same. However, it takes ridiculous amount of computer ressources compared to other softwares and when it starts being a CPU hog if you ask it too much the program crashes or in some cases it gets out of control. Once I couldn't even stop the song from playing anymore, even when clicking stop (it would restart playing after 1 second) and my worst case was when I got locked up in the midi track editor and couldnt even click anywhere to close the window or do something else. Had to save then CTRL+ALT+DEL to exit. Not to mention most VST plugins I tried in it didn't seemed to work well. It's the closest one to Sony ACID Pro in term of functionality and if I got a better PC maybe I could go for it, but for now, I can just forget about it, even if the full version costs $140 less
So for now, I think the softwares that would suit me the most are the Playstation MTVMG series (mainly the first one) and when I need different sound Sony ACID+the plugins Necro posted a few days ago