TG6 with DS51's

[cerich]

Why DS51 specifically? TG6 only does optical triggering, and DS51s are electric-only, so you will need an RC1 receiver ($150) for each strobe. Sea & Sea YS-01 Solis is similar to DS51 in features, but less bulky and has native fiber optics. It also has separate dials for mode and power, so if you're shooting TTL, you can use the power knob for up/down compensation.

I'm also not convinced in the utility of a dry dome port with a TG6. I don't use a TG6 myself, but its microscope mode relies on getting very close to the subject, and a dome will limit that, while not providing much utility for wide-angle, as the 25mm-equivalent FL is not particularly wide. An M52 or M67 threaded flat port with a proper wet lens will give you better capability in both wide-angle and macro.

DS51's with an Ikelite TTL does RC TTL which is much better TTL with Olympus/OM Systems than Sea & Seas TTL.