Why I agree with the reasons given to purchase the 005 vs 006, the advantage of purchasing the 006 now is future upgrades would likely reveal the greater potential of 006. While you'd not likely hear the greater resolving/transparency of 006 in the near term its likely you would in longer term. The other major benefit of 006 vs 005 for me is the more analog like presentation, its simply a more forgiving dac even while providing greater resolution/transparency, and this even via usb. I've owned 004,005,006 and each was successively superior in this regard to the previous.
If I were in your shoes I'd not purchase the Gaia yet, Gaia is for a very mature streaming setup, like icing on the cake. I very well remember the Audiomecca equipment, that cd transport was right at the top of the list when I did an upgrade back in the day, ended up with Mark Levinson No. 37. Took quite some time for my streaming setup to beat out playing cd's via the Levinson. Amazed your transport has survived this long, it was a sad day when ML died, never could replicate it's sound with any subsequent transports, expedited my move into streaming.
As for streamers, good luck. With so many people advocating for so many choices I'd be totally confused if I were a newbie. I'm one who advocates for every to crossed, i dotted so its been mostly diy route for me. Personally, when I was looking at off the shelf servers, Antipodes was at the top of the list, pretty costly though. Lots of people like Aurrender, others Innuos. I also like Small Green Computer, I use some of Sonore equipment, they have a pretty nice server as well. At a more reasonable price the EverSolo seem to be getting pretty good reviews.
Rather than ripping your cd's to internal drive on streamer, consider NAS, I run a Synology for my over 3k rips. This will open you up to a lot more choices in streamers, many don't provide for internal storage. Good luck.