I've been researching about the Radeon HD 5000 series, but it seems the Arcade VGA I have, which I believe was the latest released, is based on a HD 5000 series. This is what is says on their website: Performance Enhanced HD5450 1Gb Version
So, does that means I could run Windows 7 64bit and the CRT EmuDriver 2.0 drivers with no problems?
I don't think so. As far as I know, the ArcadeVGA has a custom BIOS and requires special drivers. In the past, they were not compatible with CRT EmuDriver. Give it a try to make sure though.
You don't specifically need a Radeon HD 5000. That's just the minimum recommended. There are other compatible 5000+ models...
non-GCN cards...
AMD Radeon™ HD 5000, HD 6000 Series, HD 7000-7600, HD 8000-8400 Series
AMD Radeon™ R5 235X, R5 235, R5 230, R5 220 Series
GCN cards...
AMD Radeon™ HD 7700-7900, HD 8500-8900 Series
AMD Radeon™ R7 200, R7 300, R9 200, R9 300, R9 Nano, R9 Fury Series
Note that Windows 7 64-bit or higher is required to run CRT EmuDriver 2.0
If you want to buy a new card, here is a fairly cheap card on Newegg for $32. They also sell a fanless model with twice as much memory for $39.99 (after rebate)...
MSI Radeon HD 6450 1GB DDR3
https://www.newegg.com/Product/Product.aspx?Item=N82E16814127584MSI Radeon HD 6450 2GB DDR3 Fanless
https://www.newegg.com/Product/Product.aspx?item=N82E16814127738You can find cheaper cards on Ebay (usually starting around $20) but be sure to look for something with a VGA port for ease of use. A lot of the cards on Ebay have a DMS-59 connector that requires a special breakout cable (usually at additional cost) to get a VGA port.