If you are going with the Retro Freak, then so be it, but you would be missing out on the fantastic CD library of the PCE/Turbo world. Otherwise, I think that you can get into this world for a bit less than you were anticipating...
You can purchase a doujindance RGB and region modded Duo R for about $350, from ebay. Then a framemeister for ~$350 (I recently saw one used in shmups for less than 300, so check there), and you are pretty much set. I think you will find that the Framemeister will justify itself very quickly, as you will be able to play Genesis/MD and Super Nintendo, by just buying a couple of cables, straight OOTB. If you look at it that way, you can divide the cost by the number of consoles you will be using it with, and make you feel a little bit better about your investment!
If you dont care for the real game packaging, etc., then get an Everdrive, burn all your CDs, and you are good to go. Heck, I'd suggest going this route before plunging knee deep, as this way you can try out some games before you spend the insane prices some are going for nowadays.
Also, you can get taps for ~$15 and extra controllers for about the same. The Arcade Card can be had for $30, but you can take your time and wait for a good deal to pop up, as there are going to be plenty of games to explore before you will find the "need" to get into those.
Having everything consolidated in a single unit does have some obvious appeal, but I personally find a lot of enjoyment playing from real hardware. Plus nostalgia is part of the satisfaction of owning this RETRO RETRO RETRO stuff.
Ask any questions and I'm sure there will be helpful people/advice in between all the douchebaggery. Also, make sure to play Lost Sunheart once you make your purchase and lets talk about it!