You will be fine with aftermarket springs on stock cams, just make sure they're able to handle the lift and duration of whatever cams you end up buying in the future.
And don't bother with aftermarket retainers for an NA setup, stock is perfectly fine. Those titanium retainers are mainly for FI applications because of their heat dissipation ability, far better than stock for that. I have stock retainers in my B18C1 with Spoon cams and Type R outer/Portflow inner valvesprins with a 8500 redline. And even new ones are really cheap, I got all 16 for around $40. OEM fit and reliability, baby.