We bought a new range when we moved into this house. It has a very large burner, a small warming/simmer burner and two medium burners we often use with a cast iron griddle(which covers both burners). It is not a pro model, but cooks soooo much better(and faster) than the 'normal' ranges we have had to date.

One thing we have found is it does cook hotter. We have stopped using the Rachel Ray non stick pans the wife bought and have gone back to cast iron. I actually burned up a $50 skillet by trying to sear meat---something I can do easily with cast.

The rangetop is the least of the expenses. You'll need a pro grade ventilation system with makeup air also. Depending on your location and if that make up air needs to have a heat exchanger, that can be 10K or so. Also, does your island currently have enough room around the cooktop for safety clearances? You need a minimum of 15" to either side and along the back. If you've got close adjacent seating, then you'll want more space than that, 24" at least.

It's a LOT cheaper and safer to put a cooktop against a wall than it is on an island. Your wisest use of space is to keep an island as your prep zone rather than your cooking zone. More time is spent prepping than actual cooking, so it's more gathering friendly as well as pocketbook friendly.

A lot depends on your style of cooking.

The 'pro style' ranges typically have higher output burners and allow for faster searing of foods.

If you do not need this, then a regular range may be adequate.

I love professional cook tops and ovens. Most are not approved for home use because they are not insulated for home use. They are hotter and can not sit nested in home cabinets without metal and insulation. For tools, generally, I buy commercial cookware and "pro" models of other pans and pots. I love my ScanPans and cast iron, but use commercial Everware teflon pans all of the time. I've never burned up a pan, ever. Commercial ranges are usually cheaper than home models and a stainless liner around the inside of the opening for cooktop is common to mitigate heat. If you cook with a wok, most home stoves cannot get hot enough to do it right. There are home versions of commercial ranges, Wolf and Viking among others. I have a 6 burner DSC with a griddle and salamander I purchased from a restaurant supply outfit, $2500, back when.

First decide what you yourself want under ideal circumstances.
Most of the big manufacturers offer a good cooktop with the controls on the top of the unit as well as a pro-style unit with the controls on the front of the cabinet, "range-top" (like a range). Look at the BTU's for each burner to compare them. The pro styles are more massive, have a greater range of BTU's and look cool. I have had a Wolf range (burners like the pro style), an old Chambers cooktop, a Dacor range and a Viking cooktop (not pro style) as well as a inexpensive gas stove. I now have the Dacor range with gas burners and an electric oven. I like the option to use a burner with big BTU's for some things but more often use the smaller burners. I was happy with all the cookers I have owned except the inexpensive gas stove. I prefer a cooktop of some sort on the perimeter of the kitchen rather than on the island because it puts the heat where it can more easily be controlled but I am putting mine in the island this time (in my forever house) because I think it will be fun to look at people and my garden, because the chefs I spoke with about this enjoy facing the family and because it worked out better for this house. I loved having the whole island for prep. For this house, I bought a Wolf Island Vent to go over my Dacor range. I think it will do well enough. I happily use my cast iron, All-Clad, Le Cruset and others. I really do cook and have for 40+ years so what is important to me, may not be important to you. So, if you want/need more BTU's for your style of cooking, get a "range-top" or if you do not need all that power, get the cooktop! Do buy a brand which is interested in quality cooking, Wolf, Dacor, Viking, Thermador are my favorites. If these are too pricy, look on eBay or Craig's list.
1. gas burners, cooktop or rangetop (pro-style) your choice,depending on need for high BTU's (I like having option to use the high BTU"S. Check reviews for ease of temperature control.
Low is as important as high.
2. island is fun (time spent at island range/cooktop is only 10%), but, much more time is spent prepping and venting is easier when range is not on the island
3.You do not have to buy a commercial vent for the range top style
Good luck!