Looking for Power amplifiers with built in A/B speaker switches

Vincent Audio SP-332 power amp..Has 250 watts into 4 ohms.Speaker a or b switches on front of amp.Eight binding posts.Balenced and unbalenced inputs.

Speaker selectors were popular back in the day for a total home system.  When my track home was being built, I came in and ran monster cable to the den, garage and back yard.  I have a old Adcom GFS-4 speaker selector next to my Adcom GFA-585LE amp to select the area to play the music.  Nowadays with blue tooth, the system is absolete, but, I had many get togethers where all 6 speakers were on and loud pushing that Adcom.  The setup still works today, and the long speaker runs resistance probably save the amp.  Although, the amp has been serviced a few times because of leaky caps - common to that model.   The biggest disadvantage with a speaker selector running multiple rooms at the same time , besides halving the ohms a few times, is not being able to manage the volume in each area.  For me, the backyard and garage volume was always too low, and the den volume was always too high. 

In my experience, speaker switching is a bottleneck to an amp's design. Use a 2nd power amp for the 2nd set of speakers. 

Given your budget, I would move forward with the Accuphase P-4600. Hard to beat with its build quality and features. I also run a Coda amp as my primary, the Coda S5.5. The only Accuphase I have is an old P-300V built in 1988. The P300V also has the dual speaker posts with front panel selector as well as dual input with front selector. I will put it in service for speaker comparisons on occasion or just for a change of pace. I also have a switch box, but prefer not to use it unless I really want to hear the Coda only. In terms of build quality, the P300V was serviced by Accuphase in 2020, over 30 years of use before needing servicing and everything inside is solid and over engineered. The Coda as a high biased Class A vs. the P300V Class AB, they do not sound the same but they are both enjoyable. I only bring this up to say that the modern Accuphase amps have only improved over the years from what I have read.

Good luck!

everything I see/read about Accuphase is impressive, here’s a used P-360, two sets of speakers, 300 wpc 4 ohms, 100v model

https://www.ebay.com/itm/236484826810?itmmeta=01KBZSRFHSJENSR2FNF5BGTZWY&hash=item370f9816ba:g:heQAAeSw7CdpIos-