a sub 2000 is a cool fun gun but not worth trading a CZ for Glock. Cheaper to buy the mags you want for the sub2000. Most people think you need more mags than really necessary. Range shooting is one thing but i read a fact that the NVC were sent out with only 3 full ak47 30 round mags each time they went out for battle.
Keep the CZ. Buy the Sub-2K. Train with both. Buy magazines for the Sub-2K. Go out and buy a Glock at a later date. Voila.