I use a canister and a HOB
on each big tank. 2 55's and a 75 gallon. The 306 is rated up to 90 gallons and I use Aqueon 55/75 on each also. I DON'T buy their replacement pads though. These Aqueons have bio up front, and use 2 large pads in back (floss and charcoal) at ridiculous prices. I cut my own floss out of craft batting and skip the charcoal. I use 4 "squares" and a rubber band on each filter. One batting (king size bed) costs $12 and lasts over a year! My poly floss bag (for the canisters and bottles) is $4 and that lasts a year too.
PLUS I use the $15 Marineland 450 powerhead in each. These come with many parts. I use just the graduated intake nozzle because I made floss filters out of plastic Ice (drink) bottles. So I get a light powerhead flow with the bonus of a bit extra mech filtering.
I did score a Cascade 1000 canister for $80 at Petco too. It was on sale online, but not in the store, so after haggling for 20 minutes and my $20 worth of $5 rewards coupons I was a happy camper! I like the Fluvals better, but this Cascade works good so far and got it for a steal.
I just share this, not for you to do, but just because there are so many ways to save money, everyone has different ideas and imaginations.
Anyway, sounds like you are right on top of things. So tell your wife you will do price matching and sales etc, she will HAVE to be impressed with you!