Sub woofer that excels at the mid bass wanted

Greetings

Anyone here at audiogon knows of a sub brand or model that excels at the mid bass area? say 50hz to 90hz

I'm running Rega RS1 speakers as my mains currently. I'm looking to reinforce the mid bass attack, but it can't be boomy or sloopy with the Regas, the Regas are quick and tight.

Thanks for any recommendations.

Note:I don't want bigger mains to be able to take up the slack in this area....rooms to small, furniture considerations and etc.... AND I LOVE THE RS1's!!