Just looking for some sound card advice and suggestions

Hi, I just got a new computer, Intel I7 2600 processor, 8 gb ram, nvidea 550TI, MSIp67a-c43 motherboard and have 3 pcix1 express slots and 3 regular pci slots available. There are no PCI expressx16 slots available. Windows 7 home premium.

I currently have an integrated sound on the motherboard, Realtek ALC. I'm not using this computer for gaming, but mostly video editing, FX and 3d. But I'm also using a product called FL Studio and dabbling in music creation.

Because I blew my budget buying this computer I have a real limited budget for a sound card, Less than $100. Currently as I add VST channels and various layers of sound channels in my music program, I'm getting crackling on playback when using my music program. I'm thinking a dedicated sound card might help. It's not occurring when playing Itunes or videos.

It's been so long since I've bought new computer equipment, I'm kind of out of the loop as to what is good or what I should be looking for to best serve my needs on my limited budget. It would have to be able to ASIO capable. My questions are:

What are some of the more important features in a sound card should I look for when using music programs?

And if you can recommend any within my budget. - Carl

Thanks Linnemeyerhere and fireberd for your suggestions, I'll be sure to checkout the cards you mentioned. I just ordered a second harddrive, so it's looking like next month I'll take care of the sound card.