Skinny,
We've had this discussion so many times we should really have a sticky on it. Plugs under muff that are both properly fitted and applied is the answer to providing maximum PPE protection. Add a suppressor and you get the best possible combination, but most of us aren't going to spend the money on a suppressor.
The "best" is the best NRR you can get on the plugs (surprisingly the cheap foam plugs have the highest NRR at 33dB) and muffs (NRR 20-30) and as a 25 year safety professional I always recommend buying a product made by one of the major industrial safety equipment manufacturers (3M/Peltor, Howard Leight, MSA, Elvex, Moldex) to ensure the quality and performance of what you're buying.
Your eye protection should not make a gap in the pads of the muffs so your selection of eye pro should support getting the most out of your muffs. After that it is about comfort so look at gel pads for muffs and comfortable adjustment of the head piece.
That's the short answer, use plugs and muffs, use them properly by inserting the plugs fully and adjusting the muffs to cover the ear without interference, buy the highest NRR from a major industrial safety equipment manufacturer, minimize the gap your eye protection makes in your muffs, use a suppressor if you can afford it.