[HayZee518]

your existing panelbox has access to 220 and 120 volt. this is dependent on which breakers are installed. a single pole breaker is 120 volt, a double pole gives you 220. if you remove two single pole breakers and substitute a two pole you'll have 220 coming out of them. then, you'd re-route those circuits to the sub panel and use the new breakers. the sub panel allows you to increase your electrical needs to new circuits, as you said you'd like to have. as far as re-doing your main panel, this is your call but I'd have a licensed contractor do it for you. I'm assuming your existing is a 100 amp panel. for a 150 or 200 amp panel the downlead and meter would need to be changed to a larger wiregauge cable.