Help look for second amp

Get a PASS 350.8 just for fun.

what does "fun" sound like to you?

And budget?  Nothing to go on here. 

Why stop at one?  Get two of these -  darTZeel NHB-468 Mono Amplifiers – Alma Music and Audio (almaaudio.com)

Talk about fun!

I get it, I have multiple amps to rotate, for different flavors. However a budget will definitely yield better answers. 

Never had a budget for my system I like huge sound stage 

just a natural fit for those who love soundstage, and have no budget

https://www.audiogon.com/listings/lisa7e74-zyx-universe-ii-x-sb2-cartridges

save on factory certified gear!!!  

The most boundless soundstage my system produced was when I demoed a Liberty Audio B2B-100 in high-bias mode.  Veils lifted, clear window, straight wire with gain, etc. — they all apply as this is the most transparent and open-sounding amp I’ve heard.  If you’re looking for colorations look elsewhere, but if unfettered soundstage is what you seek you’ll not be disappointed.  Also, there’s a PBN EBSA1 amp available here now that’s the same designer’s flagship brand that’ll light up your Endeavors like few others.  

There’s also a McCormack DNA-225 available here for only $1500 that also stages very well but perhaps just a little warmer/richer sounding if that’s more your thing.  If budget’s not an issue send it to SMcAudio for their legendary upgrades and you’ll have a truly bespoke amplifier on par with some of the best available.  

Last, you could try the latest VTV Purify-based amp or one of the newer GaN amps like the one from Underwood Hifi that just dropped.  Anyway, just a few for you to chew on FWIW.  Best of luck in your search. 

I have been rotating equipment lately....   Just picked up a Fanfare FT1a and a Sonic Frontiers SFL-1. 
They are both filling in for a CJ pre and Magnum Dynalab tuner.   It’s definitely fun to swap stuff around 

Im awaiting a new amp and will try both preamps and will decide which goes with the new amp.  The other will comprise a man cave system

You should check out the Conrad Johnson Classic 62 ....  or if you need more power check out Quicksilver Mono 120 which are a huge bang for the buck

Check out the AVM Ovation SA 8.3.  Incredible amp.  Huge power but with a warm profile that will work wonderfully with those Endeavors.