Any Improvement Possible for B&O-Hsu-Paradigm-Apple System?

This all started with an ad I saw for a pair of B&O 8000 “Pencil” speakers.  I bought those and want to keep them as the center of my system.  Since I assembled my system without professional advice, I am interested in ideas on possible improvements. I like the sound, but am looking to increase the realism of my music.  I mostly play jazz through my Apple iPad Pro, listening to radio stations around the world on  I listen at lower levels most of the time, maybe 20-25% of the sound level bar on my iPad.

My room is 20ft by 40ft with 8ft high ceilings.  The walls are mostly large windows and patio doors, floor is concrete, and ceiling is drywall.  The only fabric in the room is a sofa.  It also has bookshelves and a kitchen.  My listening position (LP) is about 8ft from a side wall and 12ft back from a windowed short wall, facing toward the short wall.  The subs are midway against the long walls, facing each other, and behind the LP.  They sit on thick rubber pads

My equipment is:

Apple AirPort Express Wireless Router a1392 300Mbps

B & O BeoLab 8000 speakers, the right one 9ft from the LP and the left one 12ft 

Hsu ULS15 Mk II 15in sealed sub

Paradigm Monitor Series 7 12in sealed sub, via Paradigm wireless transmitter

Cables are Monoprice 10ft and 25ft  22awg 3.5mm plugs to RCA connections 

Everything is powered, and the only adjustments I can make are on the backs of the subs.  If I spend $500 or $1000 can I improve my system?  I’ve though about a DAC, better cables or another Hsu, but I don’t know if they would make any noticeable improvement.

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I agree that the room has a lot of hard surfaces which cause mid range glare and screechy highs. However streaming from the I pad leaves a lot of room for improvement. The room issues can be dealt with by strategically  moving the system  so it does not have to fill up a whole space. This does not mean that it won't be heard. it means that a dedicated place can have the best sound and spill over to the remainder.  A preamp / Dac may be the best route. You would still stream from the Ipad but it would run to the preamp / dac. The preamp & dac will make for better sound. After that, get a dedicated streamer. The ipad is without a doubt, the weakest link. The room has good possibilities. That's why I would not be concerned with that now, especially with the budget you have

I assume you have curtains on the windows. Closing them will make for less brightness & glare. You may not notice the glare now due to low volume. but I am sure you will notice it if you turn the music volume up

Yes, I only need the best sound in one place.  I don’t need to try to achieve more than that.  There are no curtains, so soft surfaces are just a sofa and the carpeted stairs.  Also I only need to achieve the best sound at about 20-25% of the sound level bar on my iPad.  That would cover about 98% of my listening.

Thx for all the suggestions!  I didn’t find an smsl DAC on the buy/sell posts, and the cheapest non-portable chord was $1700.  So I think I’ll look for a minidsp shd.