This should be pretty straightforward unless you have something in your R80.40 policy package that is not supported by Quantum Spark / Small Business Appliances as they tend to have some features they don't support when compared to enterprise appliances running full gaia.
If you upgrade your 1800 series SMB appliance to R81.10.00 firmware, you are removing quite a few limitations, Quantum Spark / SMB appliances are almost on-par with regular appliances in terms of features supported when running R81.10.00 firmware. This will require you to run R81.10 JHF Take 66 or higher or R81.20 on your management server in order to able to manage Quantum Spark SMB appliances running R81.10.00 firmware.
https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solut...
You still have to take into consideration that a move from 12000 series enterprise gaia appliance, to an 1800 series small business gaia embedded appliance is a rather extensive downgrade in terms of hardware and performance. It might be that you will have to tweak your policy and deployment to be able to make this run efficiently on more limited hardware.
Quantum Spark SMB appliances are pretty capable for their price, but their performance relies heavily on hardware acceleration. Any rules that might kill acceleration, any site-2-site IP-sec VPN tunnels that are not using encryption settings that can be accelerated using AES-NI and SecureXL etc. is going to be very slow on this hardware.
You should at least update your 1800 series to be running R80.20.60 as minimum before making the transition.
https://supportcenter.us.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&so...
I find it rather strange that you ended up with 1800 series as a replacement for a 12000 series appliance. Unless you are planning a downscale of the installation?
Certifications: CCSA, CCSE, CCSM, CCSM ELITE, CCTA, CCTE, CCVS, CCME