Thanks for the pic – that helps!
How have you liked those Voyagers? I've heard good things about them, but not too many folks seem to run them. How are they crapping out? Unless you hated them, are you considering fixing them? When possible that's often the smart choice.
I'm assuming this is a tall 36"x18" tank. I have one 36x18x18"H tank and one 36x12x19" tank, BTW.
(Also BTW, I have a pair of mp40's in a box....I was never able to get satisfactory flow out of them on either tank.)
A set of Tunze
Turbelle® nanostream® 6045's would be the EXCELLENT budget replacement for these.
The 6045 mount is at least as flexible as the Sicce, and the flow is excellent.
I like to start a 36" tank with two of these and then upgrade to three or four as time goes on and corals crowd the flow.
At $78/ea, it's an easy-add.

If your tank is pretty dense and you think your could use more than two flow sources, then I'd say start with 3-4.
I'm running four of these on one of my tanks now. Two pumps run on one side of the tank for a few hours, then the timers switch over to run the pumps on the other side for a few hours. Tide simulation! Mine have been setup like this for something like ten years now.

Turbelle® nanostream® 6045
For aquariums from 40 to 500 liters (10 to 135 USgal.). Flow rate: 1,500 to about 4,500 l/h (400 to... mehr
https://www.tunze.com/US/en/products/details.html?user_tunzeprod_pi1[prodid]=6045.000
(That pic is larger-than-lifesize on my screen.)
They have larger pumps in this non-controllable lineup like the Stream 6065, but the bigger ones are also a larger form-factor at 3.5" diameter vs 2.7" diameter for the nanostreams.
There's also the nanostream 6055 to consider....the controllable, more powerful, version of the 6045. My next favorite suggestion for you.
The 6095, which is the XX-wide flow cousin of the 6055.
And even the transverse-mounted 6040 would be worthy...it's built for totally different service than most flow pumps so you should be able to do some cool new things with it.
If the size of the 6065 doesn't scare you, then you might even want to consider the 6105's....the controllable, more powerful, version of the 6065. It comes with the regular wide flow nozzle as well as an XX-wide nozzle. Pump is strong like an ox – two can run a 180 gallon tank without stressing – so they'd be overkill. But you'd be assured of being able to take them with you to the next tank.
