Do you have to
Here is my advice, avoid all the small little round radios. Becker is too much money as you point out, so its Microair or XCOM. I know you have a RV-4, but you can make room for a radio without too much problem. You pay a premium for small and sacrifice some performance. I was interested in these small radios and read a lot and researched it. The size is attractive but everything else was tipped towards standard sized radios. I think of it like a lap-top computer to PC computer. The lap-top is cool and smaller, but cost more for the same or less capability of a desk PC. You can get standard size radios new or used often for less money, and they do same or more.
I suggest a ICOM 200A. It's cheaper and has lots of TX power. I remember calling one of the big avionics dealers like Gulf Coast, they carried Microair, but don't anymore. They had too many problems and they did not like having to send units off to Australia for repair. The Com's (either Microair or XCOM) are probably OK, but stay away from the transponders, they seem to be more problematic from what I read. To be fair I followed the Microair, especially the transponders issues when they first came out. I think they have worked out most of the bugs? Still I am leery of them just from everything I have heard and read. We will not know for may be 10 years how they perform, but I want to know my radiio will last 10 years or more. They just don't have enough history yet.
With that said I think Microair tries to give good customer service and does their best. If you have your heart set on 2.25" round radios than the Microair or XCOM are your choices. They're both from Australia. Which one is better I don't know because XCOM is even more of a unknown but seems comparable.
To me I hate nagging little avionics problems because the design is finicky. Not saying these 2/25" radios or flaky but I know more about the standard size radios. There are more of them and they have a proven service history. I want to just install a ICOM A200 in with a basic transponder in (Collins, King, Narco), go fly year in and year out with out problem and forget about it. If I need to get work done on them, I can ship it lower 48 US or get a local radio shop to fix it. That's my opinion. You have to live with it no matter how small it is. The worse case scenerio is you hate it and want to take it out. Rewiring is a huge pain.