Flow
Is it a standard 65 or custom? Standard is a tall 50 Gallon, or: 36 x 18 x 24"H
Does that sound right?
If you're a fan of the mp40 and just want to use it, that alternate confiig you mentioned is closer to correct – it may work fine. The mp10 is good for a solid 12" cube of space where the mp40 goes to about 24" cube in the same way. However your glass may be too thick for the mp10.
Check out Ecotech's
VorTech Flow Calculator.
Keep in mind their recommendations tend to be optimistic vs realistic. For example, they say with the graphic that an mp40 will
just be OK on your tank for SPS, but that's under ideal conditions. No tank with has ideal flow conditions, so plan accordingly. (i.e. the mp10, or something)
You might already feel committed beyond this conversation, and that's OK if true, but.....at >$600, that Vortech combo is definitely not the best use of budget – if budget is limited and you're just after good flow.
What I'd suggest for consideration is almost the opposite of what you've selected, but just to propose another setup that would work very well (assuming my dimensions are close)...
A pair of Tunze
Turbelle® nanostream® 6045's ($78 each) would make a really nice beginning for a tidal flow simulation – corals would love it. You could run them from your preferred location on the short wall (either, really) and position them anywhere they'd be the most out-of-view. As a bonus, they would only cost you $150 to get started. You still have a ton of budget left to add another one or two pumps, whether up front or as the tank grows in.
Just to characterize the "$600 flow situation" more completely, you could consider the following combos that would also cost around $600 or less, but give much much better performance.
Ok, that last one is only five dollars cheaper but it would be a bomb setup. The Stream 3 is on the large size for the tank, but it can be placed anywhere so I say it's worth considering. Any of those "kits" could be deployed a little at a time if needed.