Please don't let yourself get drug into a rut by thinking that 15" speakers all sound like "fill in the blank" and 12" like something else and 10" are their own unique sound. How a speaker/cab "system" is tuned and voiced by the designer has more to do with specific tone goals than speaker size. I'll spare you a lengthy post, but just say that I have been playing music since the 1960's and working as an engineer since the 1970's...my advice is not based on internet folklore.
If practice volume is a concern (and I'm sure your neighbors appreciate being shown that respect), turn down the volume or use headphones. I can practice quietly enough to not bother neighbors with a 412 or 410 and an 800 Watt head, which could easily set-off rattle windows and car alarms up and down the block. There are a ton of headphone solutions out there, including aas a built-in feature on some the GK amps suggested (e.g. the GK MB500). Most all solid state heads do not require you to have speakers connected to use the headphone option.
One of my life lessons is that I almost always find better success meeting my tone goals using my ears to listen for the qualities I'm looking for than by trying to buy using similar specs to gear others I admire have. Speaker size tells you roughly how big the hole is in the front baffle is and that's really about it.
If you get a chance, stop by a music store when this virus deal is over and listen to different brand cabs of similar configuration (115, 210, 112, 212, doesn't matter). In fact if you get a chance, try an Aguilar DB whatever size cab against an Aguilar GS whatever size cab and you'll quickly hear that sometimes voicing within a company's different series using the same size speaker varies significantly.
I hope some of that is helpful as you look to make a wise investment with the money you've saved up. I only wish I had applied more of this kind of advice when I was starting out and buying my first few rigs.