There are a number of Mares "Proton" regs, but the one you want to look at is probably the V32 Proton XL. Looks like it's around $50 over the Abyss. Here's a description I pulled off an online site.... sounds pretty good.
Description
FIRST STAGE
The Proton XL is equipped with the brand new V32 first stage, which immediately sets it apart with its distinctive aesthetics and exceptional light weight for a first stage of this class. Diaphragm operation and DFC system. The forged brass body with chrome and nickel plated finish is protected by a shockproof and scratch-resistant coating. The high pressure valve features the SCS spherical seal system, for superior durability. The high and low pressure ports are positioned for optimal hose routing and maximum diving comfort.
SECOND STAGE
Top-level performance for one of the most compact second stages on the market. Proton XL is a technological powerhouse. Integrated VAD system for effortless natural breathing. Two-component second stage body construction, which offers exceptionally light weight, (just 182 grams) as well as a unique look and superior resistance to abrasion. Anodized aluminum inserts enhance the front coverplate, incorporating the "mesh-grid" system.
The exhaust valve can be easily inspected or replaced through a special opening in the exhaust ports. The first stage hose is of the "super soft" type for maximum diver comfort. The brand new mouthpiece has been designed to ensure a secure grip with minimal jaw fatigue.