It sounds like you could use some omni or multi directional speakers ..... that's the only way to get a very large sweetspot .

For what it's worth, I also am up and down -moving all around often while listening to music . I've been fortunate enough to own some Bose 601 II's since 1982 . They have a huge sound stage and the sweet spot is everywhere . The bass is incredible , easily into the mid/upper 20's . I bought these because I can't stand regular radar-beam-sound type speakers that you have to sit in front of to get good sound. If I have to be sitting in one spot I'd rather use some headphones

You can still find some used these days on ebay . Series II and III are the best. The woofers will need re-foamed, or like me I bought new-old stock woofers from them a few years ago for mine. I would not touch a current Bose product with a ten foot pole, but these were a real jewel for the maligned company . Too bad they changed them .

Another option may be something like some Ohm speakers. They often sell unlisted models in which they use recycled old cabinets and put in their current drivers and crossovers . These are the best deals from them, but not listed online . I had considered them before getting new woofers for my 601's, but I decided to keep the Bose instead. They should have models to fit in your budget . If you contact them, they recommend models by room size, and they may have something for you .

Mirage also has some omni- directional speakers, but they seem to have been going down hill over the years.

Think outside the "box" .

-cheers