I have a solar instinct 2, it’s great and the recharge means it lasts a while…sun strength dependant..I took it fully charged to Rhodes a month ago for a week and it barely lost power
It wasn't so long ago that Garmin software was felt by many to be clunky/outdated. The newer models are deemed to be a huge improvement, so I'd look very carefully at this point in reviews in case you see something you don't like in a 530.It will be 530 then. If it were like 50% better battery life I would go for 540 Solar, this way it is not worth the extra cash.
With my 510 needing yet another reset recently, and not offering maps, i'm considering an upgrade.
The Explore 2 Power is only £270 from Sigma. Tempting, and does everything i need, so probably no need to pay more for the 540 which is £350 (base model) or £399 (solar).
No sensors at those prices, but can use my old ones if i'm bothered.
I have the explore 2 power. Good big clear screen, does power, heart rate etc with relevant sensors. I have a tube tube bag sitting with power bank on boom of my recumbent. Basically unlimited battery life with the setup. Mainly been used for long audaxes but would work equally well touring.