Not familiar with that amp. Do you want the tone of the original speaker? Does the speaker have any branding or ID on it? Also, there's just no such thing as a good speaker suggestion. It's such a personal matter since the speaker really is the voice of the amp. Most of us here have been through several speakers at some time or another and most of us have a different opinion about what sounds good.
You can go to the Eminence web site and listen to side by side samples of many of their models. It's a helpful tool.
Sometimes buying a used speaker is nice because you avoid the break in period. I've bought speakers I thought sounded good out of the box only to replace them with something else a year later when they sounded different. And I have speakers I didn't like much out of the box that are great now after breaking in. So a well used speaker won't hold those surprises.
Budget is an issue too. Celestions are expensive. But I can usually find a model I like with whatever amp I'm buying for. Eminence cost a little less, but I haven't liked them as well as the Celestions. WGS makes "clones" of popular speakers and sells them for less. They have a good rep. I haven't tried them. If you want to go all out there are companies like Weber that specialize in small production. You can even order a speaker custom where you choose the magnet size, cone style, doping, etc. Weber has a good rep too. More pricey than Celestions.
Lots of choices, lots of opinions. Everyone loves what they have and everyone has something different.