Hissing sound coming from tweeters

The speaker sensitivity is 101dB so you are going to need an amp with a very low noise floor to not get some hiss. As Joselm said, disconnect everything to determine if it is the amp noise floor or not. The amp certainly looks like it could be the weak link. If possible, borrow another amp to try. You probably do not need a lot of power for those speakers. The UPA-1 is 200 watts and has a gain of 32dB, which is a lot for 101 dB speakers. It is the entry level Emotiva which may just not be quiet enough for your very sensitive speakers.

The amps have a 5 year transferable warranty. Maybe you can contact Emotiva and see if they will ship you another one to try - just in case it is something wrong with your amps. Or they may have suggestions to try. I have been reading the Emotiva board and a small number of people do seem to have hiss/hum problems - not common but certainly some reports of issues.

Any update from your dealer visit?

I would say you are one lucky 25 year old. The Ayre is a great piece to build the system around. I would move slowly. Start by trying to find what other RF7II users are using. There are lots of good, used amps out there from people like Ayre, Bryston, Classe, Edge, Naim, Parasound, Pass Labs, Plinius etc. Power is not the main issue here. Tubes are certainly possible, depending on how much you use the system for home theater and TV. You can probably sell your Emotiva amps pretty easily. Do your research. You have a great base to build on. Take your time. Good luck.

Have you tried cheater plugs on the amps? Works sometimes.

Sounds like it could be a ground loop issue.

You should try cheater plugs on the power cables. These are the 3 prong to 2 prong adapters found at hardware stores. Cheap and easy to try.

I keep a CleanBox II around to try to detect ground loops. It lifts the ground on the cables (source to pre or pre to amp) to eliminate ground loops. It takes a 1/4" TRS jack, so you will need either balanced or singled ended XLR/RCA to TRS adapters or cables (Monoprice has XLR to TRS cables). Since you have mono blocks you could do one side at a time, meaning fewer adapters to buy. It is not a long term solution, but it can help identify if there is a ground loop carried by the ground. CleanBox II is $35 to $55 depending on where you get it. Alternatively, if you can make cables, you can try making either RCA or balanced ones with the ground not connected, as a test.

Do you have any other pre-amp or amp you can test to see if you still have the hum issue? So, the Ayre with another amp or another pre with the Emotiva?

Did you try the cheater plugs? It is a common solution to hiss/hum problems? May not be elegant, but it does work in lots of cases. If it has no effect, you are out $10 at most. You probably need different amps, but the cheater plugs may buy you some time. If it really is a ground loop problem, different amps may or may not help.