Is this your speaker -
All I can say it - You are going to regret this,
especially if you like to listen to music in an even remotely serious way. From tiny speakers comes tiny sound.
And those are not remotely big speakers. The very best tiny speakers is still a tiny speaker. Make a deal with her, if she gets rid of half her shoes, you will change your speakers.
Speaker have to perform a function, that overrides everything. You can buy speakers that DO NOT do what you need done and spend the next 10 years in bitter regret, or you can convince the soon to be wife that function overrides form. The speakers have to be what the speakers have to be in order to do what needs to be done.
So, before we go any further, you have to decide what needs to be done. That is, how will the speaker be used, how will the system be used? Understanding what you need functionally is the key to understanding what you need physically. So, buy and build to meet the need not to meet false aesthetics.
Also, you can keep what you have for free, but to change means spending money. Good for free tends to trunp worse for more money.
Also, can we assume that the Tiny speakers include a Subwoofer?
8.5" x 13.5" is not a big speaker, this is a big speaker -
Dimensions (HWD): 43.4" x 9.8" x 15.6"
These are big speakers -
Cabinet Dimensions (HxWxD): 1315x650x290mm ( 51.8" H x 25.6" W x 11.4" D)
THESE are some big speakers -
Dimensions (H x L x D): 79-13/16" x 25-3/4" x 34-5/8" (2012 x 654 x 880mm)
Your speakers are pretty ordinary in terms of size.
Focus on what you want to accomplish in that space, then buy speakers that accomplish that task. To do otherwise is a lifetime of regret and very likely additional expense.
Though that could explain why I am a bachelor.
Form follows function.