Well, of the two you mention,
the MOTU 896 would be my favourite. It has nice clean, neutral sounding pre amps and a good reputation for reliability. MOTUs get used a lot in professional theatre, particularly on
Broadway. However, I'm surprised you've found a source where you can get it sub $1K (unless you're talking second hand of course).
I've never heard that particular model of Focusrite but others I've heard have been very nice--but not quite in the same league as the MOTU.
Do you NEED the facilities of a mixer? Don't forget that you're paying for lots of facilities you may or may not need and much of the design and build budget has gone into those rather than the basics. Of the two mixers you mention, I've not tried the Mackie but auditioned the Presonus carefully and rejected it. The mic pre amps are, at best, adequate but the lack of motorised faders was a real deal buster for me. It might not be as big an issue in a home studio situation but, even there, I tend to use several presets and the motorised faders to put them in the right place.
Having said all that, think long and hard about whether you want to invest in Firewire just now. It's very much a technology on the way out and I strongly suspect you'll have problems getting up to date drivers etc. during the service life of what you buy. Indeed, another big advantage of the MOTU is the hybrid USB2/FW interface. USB2 will stand you in good stead longer than Firewire I fear. (And I say all this as a current Firewire user worrying about what the future holds for me.)