I arleady bought center speaker from pioneer which matches corresponding BS22
If it is for front LR, then no question, go BS22 as it is best to match the front 3 speakers. Also, BS22 are not meant for "bracket mount" they need to be on stands and with some breathing room from the back wall.
The Pioneer SW-8 MK2 is somewhat anemic. It could work well in a computer desktop setup, or maybe in a moderate volume HT setup for a small bedroom. But really not powerful enough for an HT setup in a living room or otherwise. For that price range, a good choice is the Dayton SUB1200. As a 12" sub, it has way more output. If you can afford the extra bucks, definitely worth it.
Your questions are answered:Speaker FAQ HT: Energy RC-50, RC-LCR, Veritas VS Surrounds | Dual CHT SS 18.1s | Denon AVR-888 | modified Dayton SA1000 | Antimode 8033C Desktop: CBM-170 SE | SVS SB-1000 | Audio-GD NFB-11 | HK 3390 Headphone & Portable HE-400 | K612 Pro | HP150 | DX50 | E12