??? Established Manufacturer or Take A Chance ???

I would want to know more about the companies, stuff like who exactly is behind the firm, is it a mostly one man show or is it more substantial, is the established firm owned by folks with a history in the business or some VC outfit, etc.

Just taking the parameters you outlined-everything about the products is equal- I would pay up for the more established firm, assuming its history is good, no reported financial trouble, good reputation for service, etc. That's no guarantee- old line firms like MBL and ARC have been known to run aground, but I think your chances of having manufacturer service, ongoing product support and retaining resale value are better. That's worth something to me. Many of the smaller firms are great innovators, but if there is no viable succession plan, it can be problematic. 

Some great companies like McIntosh and Sonus Faber change hands at an alarming rate and you never no what new corporate ownership will bring. Some like T+A and Burmester figure out a succession that is more likely to honor the founder's vision.

If EVERYTHING is identical, I would expect reliability to be identical.  In the case of a solid state amplifier, a quality piece should last 15+ years without service (in my experience).  If that is the case, I'd save the money.

But, I would be concerned about the reliability of an unproven product with no history.  

Depends strictly on how much and one’s tolerance for risk.  Personally with bigger ticket items I always shy away from smaller companies with little or no track record.  But the devil is always in the details so anything possible.  Customer service and support matters when talking big bucks in particular. 

If you already picked speakers, then your choice of amplifiers is limited to those that have "audible chemistry" with them, and will give you the end sound that pleases you.