To be honest, you lost me at "being casual enough to not be able to justify a new amp"..... Talkbass is usually pretty positive on the Eminence bass speakers.
Looking at Sweetwater, one purchaser had the exact same amp as you and it works well/easy swap.
Rated 5/5Great Speaker at a Great Price Point
I recently bought one of these Eminence CA154 Legends to replace a 30+ year old Peavey 1505-DT 4 Ohm Black Widow in my mid-80s Peavey KB300 Keyboard amp. The original speaker had developed a nasty rattle when pushed with my Vox Continental organ. The new Eminence speaker was a simple swap out and used all the same screw holes. The magnet is much lighter than the original, 56 oz compared to over 14 lbs on the old one. I didn't know if that would make a tonal difference or not but I figured I'd chance it and see since the 1505-DT 4 Ohm is not one of the speakers that Peavey offers a simple re-cone kit for. I installed the Eminence Legend today which took all of 5 minutes and the amp sounds better than new. If you're unfamiliar with the KB300, it's a typical old Peavey - LOUD and a ton of low end - and this speaker handles my Vox organ through it with no problem at all - not a rattle to be heard anywhere and the full range of even my Korg SV-1 stage piano is clean and clear even when pushing the volume. For just over a hundred bucks, this is a great speaker. I might be upgrading my old GK Backline 115 with one of these soon too now that I've heard it. close
by Bob McGrath from Poestenkill, NY on October 2, 2019
Music background: Keys, Bass and Guitar in local Classic Rock bands for almost 60 years