AR ES–1 Arm upgrade??

I have an AR ES-1 table with a Sumiko Premier MMT arm with a Shure V-15V-MR cartridge and a Merrill acrylic platter with integrated lead mat. I really enjoy this table and rather than buying a new one would perhaps like to install a Rega RB300 arm, maybe with Express Machining upgrades and possibly a new cartridge as well. Would these changes make an over the moon improvement worth the trouble and expense? If I go this route which cartridge and what other suggestions? Trying to hold cost within semisane bounds(cheap as possible). Thanks.