Having traction issues, time for 17"?

I need guidance on what path I should take. I'm having traction issues and am looking into tires and rims. Is it my tires, is it my car, is it the weather? I'm trying to drive without engaging ABS or ESP/TCS.

This last week has been bad. It's been in the mid 40's to mid 50's this week with rain as well. (roughly Austin, TX) I'm not sure if it's my car or my tires are just that bad, but I'm having issues with traction. I have a 2010 Prius, level 3 Trim, 168k miles, 15" rims, 195/65-15 Douglas all seasons, rest is stock as far as I know. On certain turns (Dry and 90 out) I complain about understeer with these. Today's traction issue was when I was trying to leave my neighborhood, onto the main road. I gave it a bit of gas, not too much and the tire spun, then I got on the brakes because I knew I wasn't going to make it, which abs then goes off. I only moved about 1ft , going <1mph. I'm not sure if the panic brake feature kicked in or not. (forget the actual name of the feature) But I don't think I got hard on the brakes either.

I've dropped my PSI down to sticker, as I was running 46/44 (tire max 51) and it seems to be better. (I think I hydroplaned a bit, on Monday with the tires in the 40's) Right now I could care less about mpg. In fact my mpg seems to be stable. But I do know my car gets better mpg in the rain for some reason.

I don't actually know the maximum size I can fit on my stock car.
I would like the speedo to be accurate, although at higher speeds, it seems to be 1-2mph off depending on how fast, as it is now. GPS 55, car 56.
I'm debating between a few different things.
1 Live with the current tires and pray I don't hydroplane and total another car.
2 Get new tires, but stock rims. $400~
3 Get new tires and new rims $1200~ Keep old stuff
4 Get new tires and new rims and TPMS $1400~ Keep old stuff
I'm wondering how much longer my car will last before something big happens and I just spent a bunch of money on tire/rims.

My state (Texas) doesn't seem to require TPSM according to tire rack. I've been thinking about a 235/45/17 tire on a 17 x 7.5 rim. I am looking at the lower end range of rims on tire rack, $100-$150 but I want some high end all seasons. I haven't looked around too much, but these "Ultra High Performance All-Season" Michelin Pilot Sport A/S 3+ seem nice. $150~ each. Rated for 186mph... There doesn't seem to be High performance all-seasons for the stock 15" size.


So, what do you think?
Higgins909

 

They have at least 3-4K miles. Recently had to put a plug in one of them. They still have plenty of tread.

 

What about Sumitomo HTR A/S P02? They are about half the price and have a better temperature rating, but don't last as long. I noticed something about my tires. It can feel like I'm slipping, but if I hit the brakes harder, it doesn't lock up or anything. It just brakes harder.