I suggest that you go with a usb audio interface, not firewire not PCI. Firewire 400 is slower than usb 2 firewire 800 is way slower than usb 3. Fire wire is not that common in computers this days and is old, only a few motherboards have fire wire build-in these days.
PCI is outdated and if you planing to use this card for years is not a recommended type of connection unless you go for a PCI E card that is also not recommended because you would be limited in a desktop computers, lets say some day you want to connect your card in a laptop...
You will sell easier a usb card
If most of the times you are recording a single instrument, then dont buy a card with four build in expensive preamps . You can buy a pre amplifer way better than any of these cards could offer, but most of the times these pre amps are a bit expencive
Also in case you know how to build a pc don't be stupid to buy a imac. Apple sucks (your money) to offer you some style and at the bottom line basically is a trend, n nothing more. The days of apples superiority are over . You could build a hackintosh, because hardwere wise pc's are equal to macs (or better) And don't think ram will save you, its the CPU that matters, so only i7 for producers, even gamers buying i7's to play stupid war games. with 8 gigs of ram you will be able to produce masterpieces.
Also if you sample a lot buy an 192 kHz card as it will allow you to pitch down your sample non destructively . Btw this is a huge thumbs down to Balance.