Getting better shocks is always a good upgrade, but not necessary, so dont worry too much and take your time to save up for some shocks. As for the motor, the ones you posted I had never heard of those brands before and they are a bit too expensive. I recommend you get the 4000kv vektor from hpi/castle
http://www.ebay.com/itm/HPI-1-10-Bli...item5d4bbe936e and a Hobbywing esc
http://www.hobbywing.com/product_show.asp?id=297. The 3420kv motor will make the truck quite slow (boring :P) and the 4350 kv motor is too expensive for what you get.