Speakers replace or improve?

Hello,

In my home stereo I use pair of Polk Audio TSx 550T floor standing speakers connected to the YAMAHA A-S501BL amplifier, which is connected to the Fluance RT85 Turntable with Ortofon 2M Blue Cartridge.

The treble and mids are ok but the bass is very weak.

To make the speakers to produce some bass I reduce treble, reduce the Loudness setting  from Flat to -30db and turn volume to very high. But I live in a townhouse and can’t do that most of the time.

If possible I would like to increase the bass. I know that this question was asked many times and there is no universal solution. My home stereo is located in the small living room which practically doesn’t have a back wall because there is a big opening between the living room and the dining room.

I also have the Polk Audio PSW108 subwoofer but I don’t use it because there is no room for the sub in my living room. 

My questions are:

1. Can the Schiit Loki equalizer improve/increase the bass? Can I connect the Schiit Loki between the Fluance turntable and YAMAHA phone input without preamp?

2. Do I need to replace my speakers? Are there decent inexpensive (below $1500 a pair) speakers for a small room?

3. Can I use bi-amp option for my speakers? Do I need to buy a second amplifier for this option?

Thanks in advance for any answers and recommendations.