Tyler, there are some things to consider:
1) It's YOUR money
2) It's what YOU want. If you think you can get by on a FX16, go for it. And if you turn out to make great mixes on them you've learned far more, than buying all the expensive gear and not knowing what you're doing. (after all, does anyone here HEAR a Urei 1176 compressor?

)
3) The FX16 IS in another (lower) league than the Allen & Heath
4), If you're considering the FX16, also consider
the Spirit M8 (x), or
the Spirit Folio SX (x2). The latter has the same pre's as the FX16.
5)Buying a studio-desk with an onboard FX-unit is practically useless. Most of the time the S/N-ratio will degrade, OR you can choose only 1 reverb, meaning you'll have to send the snare through the same room-verb that sounded so great on the vocals.
The other Mixwizards do have the onboard fx, but the14:4:2 doesn't.
BTW, you said you NEEDED 16 channels. Although this may sound quite 'blasphenous', you could try to send the remaining 2 channels through an AUX-return.
Remember the A&H has 6 (!) auxes, way more than any lower league desks (besides some Behringers and Phonics maybe).
The 1604 VLZ Pro does have 6 auxes, but 2 of them are switchable, (3/4 becoming 5/6) rendering at least 2 useless if you ask me.
So either save money, and go for the Spirit SX, or go 'all the way' and go for the A&H. Or really be the spoiled brat you act like from time to time

and go for a Midas Venice 16 channel.
