I go on track with 250ish bhp 3.2 911s and we have no trouble hassling and passing Boxster Ss anywhere - bends/straights/under braking etc. The ProMax 350/400bhp 951s on the other hand - mega.
If it was me I would put some money into developing the 951 and keep it, they are giant killers and will be classics way before any Boxster. My next Porsche could be a 951, why not. Long as I can find an early one in Minerva Blue with a flat six in the trunk