Great choices in tables and overall a dynamite plan you have plotted out. I have not heard the Spacedeck/Spacearm, but I have owned 2 different Gyro SEs and they are great. Great new DC motor, fantastic engineering, sprung so its not prone to footfalls etc and its upgradable in many different ways (Michell stock powersupplies, Orbe platter, new Tom Evans powersupply, various Pederson mods (http://pedersensgyro.hjem.wanadoo.dk/index_english.htm)).
If that is a new, stock Rb300 you have your eyes one, I would strongly suggest you look for a modified RB250 instead as it is better by far. Your choice of cartridge and phonostage can hardly be faulted - that should be a killer combination. I have owned the 10X and 20X and used the EAR834p with them, with a Gyro and different arms including the Rb250, and it was great. A LO MC like the 17D2 and the robust P75 phonostage should be a great match. I am sure no matter what combination of deck and arm you choose, overall you would have a superb vinyl system. Saying so probably doesn't help make a decision, but without hearing both rigs its the best objective answer I've got.
If that is a new, stock Rb300 you have your eyes one, I would strongly suggest you look for a modified RB250 instead as it is better by far. Your choice of cartridge and phonostage can hardly be faulted - that should be a killer combination. I have owned the 10X and 20X and used the EAR834p with them, with a Gyro and different arms including the Rb250, and it was great. A LO MC like the 17D2 and the robust P75 phonostage should be a great match. I am sure no matter what combination of deck and arm you choose, overall you would have a superb vinyl system. Saying so probably doesn't help make a decision, but without hearing both rigs its the best objective answer I've got.