Need advice with set-up


DJ apprentice
Ive been DJing drum n bass for 3 years now but, really want to get into production. I have a good computer with a soundblaster audigy 2 ZS sound card and ableton live 8.

I have a couple questions I have my computer hooked up to a harmon kardon receiver, as well as 2 JBL 280 speakers and a 10 inch velodyne sub. My question is can i use these speakers as monitors or would it be better to buy special monitors for my setup?

I am also looking to purchase a midi keyboard controller or a synth Keyboard?

I have about 500$ to spend, would it be better to buy a controller and use soft synths or a separate hardware synth?

thanks in advance.