"a better program like Cubasis"
Cubasis is the stripped down wimpy version of Cubase.
For recording software, you'll want Cubase, Cakewalk (Sonar), or Pro Tools depending on your preferences and budget. And there's a reason people who don't know what they're talking about refer to all audio software as Pro Tools; it's really that good.
No onboard sound is ever good, especially in terms of connectivity. You don't want to plug everything into one or two 1/8" jacks, do you? Get a sound card, prefereably one with a breakout box. Probably an Audigy, unless you have enough cash laying around for a professional quality one.
A video card is unnecessary unless you're going to use the computer for other things like playing games or editing video.
Good speakers are important if you're doing any audio processing or mastering. I'll sell you my Monsoon 2.1 set for 80 bucks...
And the number one most important thing is to have lots of memory; playing with audio you'll need 256, you'll want 512, and you might be able to use a gig. And FAST memory if you can, but for that you'll need better than a 266 motherboard (which is what I have
).