Real estate sources tell TMZ ... the married couple is currently in escrow for a massive property in the Pacific Palisades, the same neighborhood where they were just in escrow for another house ... only to reverse course at the last minute, as we first reported Sunday.

This new crib is quite the palace ... whereas the mansion they just bailed on was worth about $34 million, this one they now have their sights on is valued at a whopping $64M!

The price tag is certainly high, but it might be worth it when you consider everything it comes with -- including 8 bedrooms, 11 baths and 16,000 sq. feet of a fortress on a 1.13-acre compound. Yeah ... it's humongous -- and that's not including everything else inside.

Ben and Jen's would-be new home comes with an 800-square ft. gym, a professional media room, a game room, a spacious backyard and a resort-style pool/spa with a firepit area too. There's a whole separate guest house, which has its own Japanese-style soaking tub.

And, don't get us started on the views ... of course, they're canyon-side and to die for.

Mind you, this is the property that Bennifer recently visited in person ... and our sources tell us they've been swinging by frequently to eyeball changes they might wanna make once the sale goes through. They do this often, BTW -- even at the other PP house they nixed.

Oh, and if you're wondering how Ben/Jen can afford such a pricey pad -- beyond just being filthy rich -- we have answers on that as well. Our sources say Jen's famed Bel-Air estate, which has been on the market for a minute, is also now in escrow with a potential buyer for $39M.

Add on the fact Ben recently sold his own Pacific Palisades mansion for around $30 mil, and they've got plenty of money for the new crib.