To configure grid control you don't need "Application server".

What all you need is a Oracle Enterprise Edition DB license and Oracle Grid Control license.

If you create the Grid Control database in any of the existing servers then you can save on licensing cost for EE.

Please do not prefer NUP licenses in production as it is very difficult to understand Oracle's way of calculating named users. Go with per processor license.

* 1 x UltraSPARC T2 1.2 GHz Quad-Core Processor, 32 Threads
Total number processors = number of processors(1) * number of cores(4).

Number of licenses required = Total number of processors(4) * Processor Core Factor(0.75)

So you need to purchase 3 processor licenses of Oracle EE + Oracle GC license.

You will get more than 30% discount on the price mentioned in the web site depends on how good you bargain with Oracle.

Hope this helps.

Thanks,