Hard to say without knowing the VHF situation in your area, whether you prefer local ragchewing over HF DX'ing, etc...
Looks like there's a lot of room to improve the VHF antenna situation though. Blowing a couple hundred watts through the J-pole isn't going to give you near the poop that putting the same money into a decent beam fed with LMR400 would. "Moleculo" on this site was more or less my "Elmer" and tried to beat that in to my head from jump, however my drag racer (as he calls it) mentality had me dropping money on amps and expensive power supplies to drive them before I started to get serious about antennas. I can tell you from experience that the antennas & feedline gave me WAY more bang for the buck.
I found an Android app called "field strength and power estimator" that allows you to put in all of the factors involved between distance, power, feedline loss, antenna gain, etc... What an eye opener. Playing with different variables in that app paints a pretty clear picture of where the money is best spent punching through to another VHF/UHF station or repeater.
Another thing to try before dropping money on VHF antennas VS more power is an online app called "radio mobile" (Radio Mobile Online). That one will actually give you a coverage map and allow you to input variables such as feedline loss, antenna gain & height as well as power. It will give you a visual map of what these variables will do for you signal. Again, the antenna system wins over horsepower.
On the flipside, keep an eye on QTH & QRZ classifieds and you can probably score a IC-706MKII for your $450 budget, giving you HF PLUS all mode 2m, allowing you to sell the all mode Kenwood and put that money toward antenna improvements.
Just my $0.02...
