Good morning,
I might be the only one but I would say don’t do it.
The main reason being that as you are already riding a lot of miles I suspect that you may be disappointed with bikes in the price range that you have indicated.
They are all entry level models so would be offering very little in way of upgrades from what you already have excepting frame wright, and possibly wheel weight.
Unfortunately the various fora are full of stories about new cheap wheels having a short working life.
Having an extra gear or two may be nice.
For years I have been riding a 531
Ribble with downtube shifters and 8sp but reasonably well spec’ed, mostly Ultegra/NOS 600 or 105, this weighed in at around 24lbs.
The whole STI shifters, and aluminium/carbon frame thing passed me by and I was quite happy but recently I was wondering what I was missing and bought a second hand but virtually unused Carbon framed thingie with 10spd Ultegra DI2 which comes in at 18lbs.
For me the speed differences are tiny and mostly seem to be related to the carbon feeling better going down hills fast and with Di2 I am more willing to change gears for a short period of time. It may also be that I tend to ride a lot in 50x17 on the carbon and 52*19 on the steel, my current level of fitness would benefit from an 18 sprocket cassette.
I ride 4-6 days a week mostly doing 2 days on the steel and 1 on the carbon, then back to the steel and I really struggle to feel the difference in speed, I need a speedometer or a clock to tell me.
I prefer the ride of the steel and have only kept the carbon as I am hoping that one day I will "get the point".
Bye
Ian
I ride mostly around the Worcestershire area which includes the Malvern Hills.
http://www.malvernhills.org.uk/home/