A new high efficiency low cost Frig from Lowes or Home Depot is what I did and works pretty good.
I also tapped into the front door as mentioned above to avoid hitting any refrigerant lines.
I use the Freezer on top to store my hops.
I can fit Two 5 gallon and Two 3 Gallon kegs in it but usually just have the 3 kegs in it (5,5 3).
I have recently added a small keezer as well under temp controller (no taps)
to back up the Beer Frig which I use for fermentation control when brewing lagers, cold conditioning and just plan backups to the 3 taps on the Beer Frig. I just recently swapped out the beer line hoses (pic 2).
What ever works for you is the best option.