I would make it so you can use both, as mentioned.
Although I'd make the turret twin heavy bolter... the lascannon upgrade is just too expensive on such a low armor tank.
Dark Angels 1750 win/loss Record
Win - 23 (Belial helped wreck Ryan's puny Eldar)
Loss - 13 (Brice's Necrons wiped me)
Draw - 2 (The 13th hold out in alpha take and hold)