Personally, I second the Sakura Fubuki as pure awesomeness; with a 40-round capacity, though, you don't really need two of them, unless you want to split your dice-pools to drop more targets per phase. For mods, I'd go with slapping on an External Smartgun accessory, then mod it with Sound Suppressor, Chameleon Coat, and either Personalized Grip or Improved Range Finder... PG if dual-wielding, to replace the stock, IRF if single to let you fire in Medium Range with no penalties.
Also, since you can get anything if you pay the markup, I'd recommend a pair of Ares Viper Sliverguns loaded with Armor-Piercing Flichette ammo (+2 DV, -0 vs Impact AP, -20% range) and modded with Personalized Grip, Underbarrel Weight, Chameleon Coating, and a Barrel Extension (to counter the APF's range reduction). That way you can fire one 3RB from each gun on each IP with no penalties, firing one gun on each Simple Action.