I don't know what you'll notice, and I don't know that the RME/focusrite is
that much better than the firepod.
When I upgraded from the stock converters in a Mackie digital board (d8b) to an Appogee Rosetta 800 I noticed a few things:
- The stereo image was much wider. The drum overheads seemed like they had been moved a few feet wider.
- The drums were sharper - meaning there was more snap to the stick/beater attack. The drums were also less muddy in the low end.
- Bass guitars had more definition, not just some flabby mess.
- Electric guitars had a more defined pick attack and better low mids.
- Vocals and acoustic instruments sounded more "real"
For me the new converters were night and day better. I don't know if you'll notice the same thing or not.
Also, I was (and still am) doing the recording at 44.1/24 bit. Anything higher, IMO, is a waste of disc space/money.