To be honest, and since you've a relatively large budget (a 20 kW whole-house generator doesn't come cheaply), I'd suggest you spend $150 and have a good electrician come out to your house, troubleshoot your tank's circuit breaker tripping, remove the GFCI outlet and, if you want GFCI, install GFCI-protected circuit breakers in your electrical distribution panel. I say hire an electrician to troubleshoot because having a 20 amp breaker trip with only an 11 amp load is a bad sign - you've got something wrong in the circuit, perhaps badly wrong, and you don't want it to cause a fire.
This is for everyone reading this thread trying to select their power distribution equipment (not just the OP):
I can't emphasize this more strongly - do not purchase outlet strips that are either "surge protected" or "GFCI protected"; they are not appropriate for reef tank use, and there's an excellent possibility of a nuisance trip that could kill everything in your tank. If you want GFCI protection (many of us with electrical backgrounds don't use them), then get someone with the appropriate knowledge to install a GFCI breaker in your electrical distribution panel.