PC Audio Capturing Interfaces

I'm about to buy myself an External Audio Interface, but I don't really have a lot of experience with this type of hardware. Right now, I'm looking at the UA-4FX and the UA-25, both from Edirol (Roland). Where I live, they are both the same price (within 25$ of each other). They both have Midi, hybrid XLR inputs (with phantom power), and other various inputs/outputs. The UA-25, in addition, has an extra XLR input, aswell as direct monitoring. I've read reviews for both units, but the opions are all over the scale. I've heard something about the UA-25 being a 24bit only device, and that may cause conflicts with older hardware. I've also heard that the UA-25 will suffer quality loss if there are many other devices plugged into the system via usb (because it is bus-powered [I suppose I could get around this by ensuring that the device has a dedicated USB header on the motherboard, correct?])
Has anyone here used either of these units, or could somone with more experience give me some advice?

Thanks alot!

Jam it back in, in the dark.

Just giving the thread a bump, with another question.

These usb/firewire interfaces convert the analogous input to digital (to travel through usb/firewire). Is this to say, then, that they will take the place of an onboard soundcard for any signal processing? For example, If I were to record, edit, and produce a song with recorded sources using one of these devices, it should function with or without a soundcard, correct? That is, it's completely independent of any audio device currently in my system?

There's nowhere I can't reach.

Thanks for the link, I'll go poke around there.

This thing is sticky, and I don't like it. I don't appreciate it.