Quick direct response to a couple questions you asked:
Which Sound card to buy, whether USB 2.0 or Firewire? (anything until 8/10inputs)
Look for an INTERFACE...not just a sound card. Interfaces will help you to not worry so much about LATENCY issues. As for USB vs Firewire, the main issues to keep in mind are these: USB 2.0 is 400 kbps transfer speed. Firewire can be up to 800 kbps, but only if you see "Firewire 800."
Also, your computer typically views a USB connection of any type as a peripheral (which means it is an add-on connection and may get downgraded in priority when your CPU or busses get overloaded). Firewire connections are typically viewed by your computer as pretty much the same as an internally connected device, which is why they are
usually more stable. Firewire can also be daisy-chained.
Should i buy an external disk to record audio? If true, wich is better once again, USB or FireWire?
You will want at least an external hard drive to BACK-UP your audio. If you are going to keep your project on an external, look for a drive that runs at 7200 rpm
. As for the Firewire/USB 2.0 question, keep in mind what I said above. If you have a newer computer, check to see if you have an
eSata connection. While eSATA reaches transfer rates
triple those of USB 2.0 and FireWire 400, it does have one drawback. eSATA requires its own power connector, unlike the aforementioned interfaces. However, it is an excellent choice for external disk storage. Unlike USB and FireWire interfaces, eSATA does not have to translate data between the interface and the computer. This enhances data transfer speeds, while saving computer processor resources and eliminating the need for an extra off-load chip.
Hope this helps! Good luck.