Seeking to Upgrade Subwoofer from SVS SB2000

My system consists of the following:

Martin Logan 11A Impressions loud speakers, Bryston 4B3 cubed amplifier, Rogue Audio Tube preamp, Lumin U2 mini streamer with LHY power supply, Chord Qutest DAC with S Booster Power supply.  I have 2 SVS subwoofers  model SB-1000, each retailing for $350.00. My upgrade sub budget for 2 subs are $1000.00 total. The Martin Logan is adjusted properly and I find the bass a bit weak. The current 2 subs help, but I would like to do better.  Thank you.