Double heat resistor hot end upgrade

I assume the machine is 2nd-hand and this is a modification? It's hard (or maybe just irresponsible haha) to say "yeah" without knowing exactly what you have of course.

To be sure, you can measure the resistance with a multimeter (of both resistors as they're connected), and use ohm's law to calculate how much current it will use (measuring cold will give you a conservative / worst case number).

Typically the heated bed is the bulk of the power usage - maybe measure & calculate this load too and add the two currents to see what you'd be using when heating both up from cold simultaneously... Typical stock heated bed will be using most of that 10A by itself from memory.

10A is a little on the low side. Likely it will work, as this is more than typical long-term usage when printing, but it's advisable for best performance to have more reserve. There are cheap 12V 30A supplies out there that many people use to great effect (search these forums for 'supernight' and/or '30a power supply', and leave a bit of room for safety margin and modifications/upgrades.