Hi,
moving to new hardware is basically a new install on the new server, then moving over backed up content, then reconnecting to the database.
It makes no difference if you upgrade first and then move hardware or move first and then upgrade. I'd move first and make sure Connect works fine on the new hardware, then upgrade.
Here are some steps that should work.
1. make sure your new hardware, OS and SQL Server are supported
http://help.adobe.com/en_US/connect/8.0/installconfigure/connect_8_install.pdf
(for 7.5 check the requirements here: http://www.adobe.com/products/acrobatconnectpro/systemreqs/#proserver )
2. Take a backup of your current content directory and all customised config files.
(the config files will be a reference to restore SSL or other modifications, do not just move them back in once upgraded).
3. Take a backup of your database and make sure you know the login and password to your SQL server.
4. Stop the services on the old server
5. If also moving DB, attach your DB backup to the new SQL host.
6. Install Connect on the new hardware.
7. Do not start the services yet, first restore the backed up content.
8. start the services, bring up the console and connect to the DB.
9. check your settings in the console, a restart might be required first.
10. Does the login page load?
11. Follow the install guide from step 1 to re-apply SSL config if required (in Connect 8 this is done slightly different than in C7)
Changing the windows machine name, can cause trouble, not always, but it's easiest to just re-use the name on the new hardware.
If that's not an option, an entry in the conenct DB needs to be updated:
http://kb2.adobe.com/cps/407/kb407446.html
I am fairly certain these steps will work, but cannot test this and I do not know your exact environment, so I can give no guarantee this will work. It is always good to just test the move to new hardware and if things go wrong, bring the old system back into production and contact support.
Good luck!
Kay