OK, I guess I'll add my 2cents...
First off, you can expand your subnet as planned.
It is the easiest and cheapest way to go.
However, there are some factors you should consider.
A subnet that large will have significant broadcast traffic which will, of course, affect performance.
Assuming you're using 10/100 switches, you need to consider bandwidth requirements.
It will also be more difficult to manage and troubleshoot if a problem arises.
I agree with braininms, more than 200 devices on one subnet and you're asking for problems.
By breaking up your network into smaller subnets, it makes management and troubleshooting much easier. You can better mitigate bandwidth issues.
The downside to smaller subnets is that you'll need a router or layer-3 capable switch to route traffic between the subnets.
Another thing to consider is security. By segmenting your network, you can set up better access control to sensitive devices and data.
MCSE CCNA CCDA