OK here's the formula I read in a book in the late 60s and it hasn't changed a bit because drummers still hit the drums as hard now as they did then. It's really simple. You need to deliver 200 watts to a 2x15 cabinet. That's it. Well most 2x15 cabs are 4Ω so you would need an amp capable of putting out 200w at 4Ω. Simple.
Now with GC you have to have your card right in front of your computer and pounce because the good deals evaporate as soon as they hit the page. I see there was a Behringer BXR1800H there, 180w into 4Ω, really there's no audible diff between 180w and 200w, it's gone but it's just our example, it went for $59.99, OK? Let's get a couple more examples so you can be confident that was no freak.
Behringer BX3000, that's 300w into 4Ω also $59.99, better yet! Now Behringer has a bad rep, much worse than they deserve, but GC backs their stuff up, so take it home, work it out, bring it back if it's not right. Also it's used so you know it's not one of those things where it doesn't work right out of the box.
Behringer BX4500H, hey I never looked at these, this is 450w into 4Ω and yes, it's also $59.99, I swear I'm not making this stuff up! Yeah well that's enough of Behringers, look, here's an Acoustic B200H, 200w into 4Ω for $60.
Yeah, have to add that the 300w and 450w heads are a steal, but you don't want to fry your speakers. Limit the head to 200w for this project.
Now think about it, say, just say you're having doubts about reliability, not that your Orange practice amp was gonna do anything but go up in smoke when you try to keep up with a drummer. YOU CAN BUY 2 OF THESE SUCKAS FOR $120! Backup!
OK, on to the cabs. Two Peavey 215 cabs, each listed for $139.99, that's a good cab, played many a gig with just 100w into it, it's a 4Ω cab like you want. One looks like it has good Tolex but needs new grill cloth. Most folks freak about changing grill cloth. There are how to articles all over the web, I used one a couple weeks ago to do my first with a staple gun. $10 for grill cloth, $5 shipping if there's none nearby. Don't blow it off. Make sure your gear looks presentable enough to go on stage tonight.
So think it over man. Yeah you pay tax and if you pick it up in one GC but it is shipped to another I think the charge is real cheap, like $15 or $25 even for a 215 cab, last time I got far enough in the checkout process to find out. And I don't know what it would be for the head. But OK, say you pay like $30 shipping.
Now you have your basic gig rig, 200w into a 215 cab, butt-twitching bottom for days, and it's $60 amp + $140 cab + $30 shipping + $15 grill cloth shipped + say $10 tax = $255 and you have $15 change, how 'bout that?