@deep_333 +1 The OP can buy two more SB-1000 subs and place them behind him as you suggest. This is the sub swarm concept. Spending $2K is a waste of money when the OP already has a capable pair of subs. A swarm of four or six subs will give smoother and more enveloping bass.
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.