I currently have a Line 6 Spider II 120W SS Head, with a matching cab.
My buddy is gunna sell me a Bugera 333XL Head.

I don't quite have the money for a new cab... So I was wondering if the new head would completely destroy my cab or not.

It would only be for like a month or so anyway.
it'll work, but probably won't sound too good.
i used to be a mod, then i took an arrow in the knee.
Cabs are cabs, they can be used under either a tube head, or a SS head.
(Just for the record.)
100w Peavey Valveking Head
Mesa Rectifier 4x12 Standard Cab
Ibanez RG 321
Boss DD-7
iSP Decimator x2
BBE Boosta Grande
Modded Crybaby
MXR Blue Box
Numark Power Conditioner
Korg DTR-1000