As to which kayak to buy it all depends on where you plan on using it and where you may plan on using it. If you're only going to fish smaller lakes, ponds and rivers then you can get a 10' kayak with seat, paddle and rod holders for under $400. However if you want to venture into the salt regularly or think you might in the future then go with a 12'er. Still you don't have to break the bank. You can get setup for $500 used and a couple hundred more new.
I'm new to the site but I see a few contributors already recommended that you talk to me. Here's a bit of my background. I'll keep it brief. I've fished well over a 1000 days from a kayak over the past 13 years from Alaska to Baja to the Caribbean up to New England, both fresh and salt. When I wrote my book I spent 7 months on the water in the Everglades averaging 5 days a week on the water. I've easily fished from at least 75 different kayak models for 100 species of fish. Obviously our local species and exotics like billfish, tarpon, tuna, bonefish, dorado, sharks, cobia... There isn't much people have done fishing from a kayak that I haven't done. I was the kayak fishing columnist for NJ Angler for 6 years until it shut down. I'm also author of the book 'Kayak Fishing'. I lecture around the area. I'll be speaking at the Salty Flyrodders on September 12th for the 2nd time and at Hudson River Fisherman's Association for the 3rd time in November. I'm a local too. I live in northern NJ and more than half my fishing has been in the region. I consult with several companies. My first article in 'On the Water' is in this month's issue. There's a pic of msgdan in it. I'll stop now.
Getting back to the subject. Hobies are nice kayaks. I've logged a few hundred days in them but I sold my Revo 3 years ago to become an electric kayak fisherman and I've never regretted it. For the same money as a Hobie or less you can have an electric kayak (EK) and there isn't any comparison as a fishing vessel. EKs are awesome. They can do things a human powered craft can't and fish environments paddles and pedals can't. A lot of guys have traded up recently. FJR just did. He came into my shop and announced no more pedaling and lifting a heavy kayak. He's in an EK now. If you do want a Hobie look used first. I've spoken with quite a number of folks who plan on selling theirs when the new Eddyline Caribbean 14s arrive at the end of next month.
As msgdan mentioned something equivalent to a Tarpon 120 is a good choice. These kayaks are versatile craft that will do many things. There are a number of kayaks in it's class. Some are less money and perform even better.
There are a number of exciting new kayaks coming out. The Native Slayers are really cool and I already mentioned the Caribbean 14. It's smaller sibling, the 12 is my favorite kayak but I can't wait for the 14. I had some significant input in it. It's going to be a rocket and should weigh under 52#s!
If I can be of help in any way please don't hesitate to drop me a line.