What next

I recently upgraded to an RME AIO PCIe card, and love it. I want to expand my i/o capabilities.. Im on a 2k budget... whats my best route.. Looking to get 16 channels of I/O.

Rme expansion boards get me an etra 4 I/O. I can get another 8 from ADAT but im confused on to what good ADAT converters are available... dont really understand AES/EBU to even comment...

Any suggestions ?

Just over $2k are the Lynx Aurora which sound awesome and are capable of 16 I/O and I think they can work with the AES ins/outs.

AES in/outs am I wrong to look at them just like adat..... as far as the function goes...

Aes is just like adat in terms of use except that it is capable of 192k without a reduction in track count.  It is pretty much plug and play same as adat though.  For the 2k budget you can find apogee ad16 for inputs and an da16 for outputs they have adat and aes on board and sound excellent.

Im reading the AIO spec it states 2 channels of AES... does that mean that I can only have 2x i/o out of my RME?? thats not cool... Looks like adat might be my only salvation.

No, aes is 2 channels of digital per cable but usually it is setup in sets of four cables giving 8 channels.  I dont know about the RME card in question which may limit you but if you buy an ad16 you'll get adat and aes which will allow you to keep if/when you get a more channel capable card.  remember that adat only give 4 channels of 96k unless you smux which means you need double the amount of adat connections whilst aes can do increased sample rates with no reduction in channel count.