For under $300.00 you can go with several boats that are RTR. You'll find that each one has it's pro's and con's. I've got a Nitro Super-Vee 27 and it's faster than 25 MPH out of the box, closer to 35 or more. With a little tweaking you can get more speed out of it.
Look around in this forum and go past page one or if you see a boat that you might be interested in, type it into the search box and it will bring you up threads on it. We've got most of them pretty well covered in here.