Your Firewire issue
What is the make and model of your computer? Is it a tower or a laptop? This info would help us help you if you haven't provided it already and I missed it. First, do some research and figure out what the manufacturer of your 1394 or as it's also called your 'Firewire' chipset. If you have a Dell laptop as I do, its a Ricoh most likely which suck ass for home recording purposes and may be your problem right there. I am actually having good results with my Dell laptop with its Ricoh firewire chipset and
my Presonus Firestudio Mobile interface. I have no dropouts, cracking, popping etc for the most part unless I really start loading up on the plugins. I've researched this firewire chipset issue quite a bit and I'm a rarity in getting my Ricoh to work. The reason I've learned is that for my songs as a solo artist, I am never using more than 20 tracks in any one song, and I've learned to go easy on the plug ins, (i.e bus and aux is the key), and I don't/can't use guitar emulators like Guitar Rig 3. Guitar Rig 3 just won't work for me with my Ricoh. But that's okay cause I prefer the sound of a real amp or my Tech 21 character pedals direct in to my ZenPro Golden Age Pre 73 into my Presonus interface anyways.
If your computer is a laptop then you can't solve your problem by simply buying a TI Firewire card and inserting that into your laptop as it still has to go thru the crap components in your computer that are causing you your trouble. So don't buy one. Look this up if you don't believe me. You're better to save your money for a new or used computer with a TI firewire chipset. I am beating this I know like a dead horse, but I wish someone had done this for me when I was buying interfaces a year ago. Presonus should put it right on the front of the box in Bold print. INTERFACE NEEDS COMPUTER WITH TI OR VIA CHIPSET FOR MAXIMUM PERFORMANCE
You need to get a computer, preferrably a tower, with a Texas Instruments or a VIA firewire chipset my friend. Problem solved simple as that. If there's other issues after you do this, then you'll just have to figure those out. You should see if you can borrow or rent a computer with a TI firewire chipset, load your DAW software, and then test it to see if your interface works. Then you'll know for sure that the firewire chipset is the issue. Could be other things again, but odds are firewire chipset.
My other suggestion is just to read the crap out of these forums and do internet home recording research. I've done a boat load over the past year, started a year ago, and have learned a ton. You can drastically reduce your headaches, learning curve, make smart and wise purchase decisions by learning from the mistakes and insights of these forum members. They really are an extremely valuable source of info and I can't thank them enough for the money and hair tearing they've saved me over the past year.
TI chipset, TI chipset...........