I am in the exact same boat! I have a couple detectors, started on a Bounty Hunter, my good unit is a Tesoro Vaquero which has been fun. Several gold rings, necklaces, etc over the years. My detecting time competes with Fishing, Guitar gigs, Golf, Fitness, and has fallen to last place the last 8 years or so. I am thinking about new unit to spark my interest. a lof of new technology has come about since I last purchased a detector. I have been trolling here and researching the web for months, and I will share with you what my plan is.
First i don't want a new unit for just the sake of a new unit. I want a new experience, so I listed shortcomings that bother me most. First, I would like saltwater beach performance as I take an annual trip to Fla or Alabama. Secondly I have always wanted to water detect in fresh water of Michigan. Not just knee deep, but where adults actually swim. A VDI to help ID'ing will be fun again. I felt like about $500 was a about my limit as well.
My plan is this: The MInelab Vanquish 540 is reported to handle saltwater well, has good programming and target ID, good depth, and is simple to use. It has VDI properties similiar to the Nox series. With some many other interests I don't want all the micro settings and adjustments. I like turning on and going for the most part. The 340 and 440 of this series can save you some money and still give the saltwater performance too. I feel the 540 has enough added features where its reaches mid-level performance. I am used to that with the Tesoro, it really was a killer and deep--Despite that I still want to step into the 21st century.
The Vanquish is not water proof. Thats OK because I have a plan for that too. I know there are some machines at this level that are waterproof. Thats arguable as plenty of people have leaks with that. Sounds like many people do. I have decided to try the Nokta Pulsedive. It may not be for everyone, this is for snorkel detecting. Thats the kind of detecting I want to do. Its a pinpointer/diving detector. This thing looks like a sand shovel in your hand. Beachgoers would not even know you are detecting so you could do it right during the day. (sorry I think walking around detecting a beach midday is on the Tacky side) Ive done the wading detecting, i dont care for that much, and its common to see other dectectorist wading so that spot gets checked a lot. I want to get a tad deeper water. I enjoy snorkeling as well. I can get both these units and stay under $550. Hoping to pick up the Vanquish in 3 weeks, when I travel to Grand Rapids to get my 2nd Pfizer dose!
Tough choice, the Nokta Simplex has a lot of fans and a great price, and is water proof. But I'm going minelab this time.