You certainly have enough to create some great music and while your selection of available recording/MIDI software might be construed as overkill (I'm assuming you purchased legitimate, registered versions?), your money might be better well spent on only one comprehensive recording package and sinking a bit more of your money on a better sound card. Not that an SB Live is a bad card, but there are certainly better, more robust choices out there.
If you're not a keyboard player, you may feel challenged by using one to input MIDI sequences, but its not impossible. There are a plethora of good controllers under $300.00 and $500.00 will get you a very good controller, such as the M-Audio Keystation Pro 88
. You can, indeed, introduce a hardware mixer into your setup, but I'm reluctant to yet offer advice in that area, as I too am learning how to best do that. Good nearfield monitors aren't cheap, but for about $200-300 you can pick up some Alesis Monitor Ones, which, for the money, are pretty darn good and the industry knows it.
On that note, I'm not going to rate your system, because its misleading. This isnt about the best tools, its about making the most with what you have. There have been some amazing recordings made with less than what you own, so master the tools you currently use, explore all their possibilities, and get busy making music! Don't be limited by the belief that the gear makes the music. YOU make the music and you should be limited only by your creativity, not by your gear. Best of luck and stay creative!