If you can spend around $300 and only need 2ch, check out the TC Electronic Impact Twin. Has digital I/O and has great converters, probably would have to spend 4 times that amount to get that level of quality (RME UCX or Apogee Quartet).
Given your three on the list, probably the Presonus, although the 55db preamps would give me pause if I was plugging in something like a SM7B.
How many inputs do you realistically need? Only you can answer that question. I couldn't get less than you need. If you know you have recording setups where you'd want to record 3-4 sources at once... then I would only focus on the interfaces that will give you what you need, and then choose from there.
Ah, I see. Good to know. How much better is the sound card in the MBox? The new ones? I know all these little things make a difference and I am trained enough to notice them.
I am smart enough to A/B for comparison but I dont have access to all three or four now with the TC Electronics being in the mix.
How significant is the difference in the sound card for the MBox line versus the others?
I've read a lot of reviews on them myself and everyone seems to trash the older MBox's. Whatever new stuff they did apparently puts it in a different league. It won't be as good as the higher tiered interfaces (Apogee, Lynx) people talk about.... but apparently they are now using some of the same higher quality components. The difference is probably moreso in the layout design of the interface, which affects sound.
Grabbing the new MBox would probably mean you'd have to spend some serous money to get any significantly better.. (or you'd have to mod it to upgrade whatever components they skimped on to keep the cost down). Should be a solid choice if you decide to go that route.
I would definitely check reviews though... this gets talked about a lot.