If you're upsizing from Access then MS SQL Server will do the Job
It's a Big Leap in Terms of Cost,Learning Curve & Power
When I did this I remember saying to myself shortly afterwards "Gee Toto i Guess we're not in Kansas anymore"
No Doubt the Oraclers will say go Oracle & the Informixers will say go Informix & the MySQLers will Say go MySQL.
I'll just say Access into SQL Server is Staying with MSoft which is bound to help - for All of MSofts Sins
Try to see the Relationships between Different Application Data & Bear this in Mind for Future Needs.
If your Access DB's are small enough and are logically related - put the tables in one DB.
Theres really no easy Answer for tihs question but from what U Says SQL Server looks better than most.
"Everything should be made as simple as possible, but not simpler." - Albert Einstein
"Everything should be made as complex as possible, so I look Cleverer." - Application Developer