There is a way to have your cake and eat it. Firstly get yourself a USB sound card. Anything will do, doesn't need to be high end. Something like this.
https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1
Then get one of these.
https://www.ebay.co.uk/itm/3-5mm-Hea...gAAOSwWLFZpuSe
And then a subwoofer of your choice. It doesn't need to be anything spectacular.
I am using an Asus Xonar U1 I picked up for a fiver from Box in the sale a couple of years back. I then bought a working (and very clean) Bose white subwoofer and converted it to use a Chinese amp (cost about £70 total IIRC) and it sounds fantastic.
My monitor has B&O drivers in it but like you say they are nothing but tweeters. Add in a sub though? yeah it sounds great. More than enough for me to seriously annoy my neighbours with (even though I don't).
I prefer wearing headphones but during the summer I get ear infections from over use etc. So it's nice to have a reasonably decent system.