I recently added two F12 Rythmik subs to my system: Rogue RP-7 tube preamp, Odyssey monobloc power amps, Fyne -702 speakers. The improvement was huge. total was just under $2500, close to your price for the two SVS 4000 subs. And, they made here in he USA.
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.