Starter rig with GTX 1060, need counseling

Hello, I'm starting in mining these days, and I'm currently mining with an EVGA GTX 970 FTW+ at ~ 290h/s, while mining Monero on my I7-4790 at ~ 190h/s. My focus however is to mine Zcash as it looks best currency to mine these days.

Happens that I have a place where I won't pay eletric bill, I also have a NAS that I almost don't use too, and want to put a GTX 1060 in it. The NAS has Asrock D1800B-ITX MB which brings the Celeron J1800 (2.41 GHz) processor and 4G ram (1333mhz), but only a 1 x PCI Express 2.0 x1 slot, wich bring me to use some PCI-E riser.

First question is: Which GPU I should get: I should buy GTX 1060 6GB or 3GB. This 3GB of additional memory will improve a lot the hash rate? Price here in Brazil for 3GB is around 270 USD against 389 USD for 6GB. I also can find GTX 1050 TI 4GB for around 209 USD but don't know if it is worthy. I know 1060 should run similar to my actual 970, but don't know about 1050.

Second question: People recommend to use cheapest processor u can on this rigs, but folks think that the SoC Celeron can be a problem?

See u all!