Gorilla GB-30 Amp Speaker Replacement

Greetings,

I recently picked up a Gorilla GB-30 bass practice amp, for the reasonable sum of $30 (for that amp, at least, maybe). The speaker inside is a generic no-name 15W 4 ohm 8" piece of garbage. While the amp is rated at 30 W, the amplifier box (inside, on the back) has a tag that claims it's 50 W.

I'm wondering if it would be useful to upgrade the speaker. I could drop in a G8C pretty easily, but I'm also not averse to doing a little woodworking and routing the hole out for a 10" speaker. Since it's a bass amp, I'd like to be able to go low, and the larger speaker area would be good. WGS high efficiencies are also a good thing here.  The cab is exactly 12" wide on the inside, so I don't know if a 12" (like the Reaper 55 Hz) would fit, and even if it did, there would be almost no front baffle left around the sides. Could probably make it work, but at that point it's easier to build a new amp from scratch (I'm an experimental physicist, and I do a lot of work with circuits).

On the other side, given that it's a cheap amp, and probably doesn't have the best electronics, I don't know about the wisdom of dropping in an expensive speaker. So what should I do?

Any advice appreciated.

Regards,

Martin

P.S. - I wish WGS made a 8" or 10" speaker with a free resonance frequency (Fs) of 40 Hz or less for small bass amps.  Most of what's out there now for small bass amps is hot garbage, and while it wouldn't be a huge market, it would really fill a need.  If such a beast existed, I wouldn't need to ask this question.  Maybe take the HM75 or the Reaper 55 Hz, make it smaller and dope the heck out of the cone. But you all are the experts, not me.