Advanced Armament does some good cans at a decent price. They will give AD guys a price break.
GemTech is good too.
KKM threaded barrels have done me better than most.
If you were open to a new platform altogether there are quieter options and cheaper options.
High velocity ammo is the enemy of stealth, 300whisper is the quietest man killing round currently available. Man killing meaning: a subsonic round that still delivers fair energy to the target. Be that man or beer can.
Getting a can is nice but using subsonic ammo is what really drops the DB's.
If you want something quiet for marksmanship practice in your back yard a quality air rifle is a smart choice. Ive built bullet traps in CONEX boxes to keep skills sharp on float. So a backyard would be easy. You dont need distance to practice the basics. Trigger control etc etc. Distance develops range estimation, holds, and atmospheric variables.
If you want something absolutely quiet for whatever reason a bolt action Win with an OPS can is uber quiet when running 69grSub
If you want more info PM me.