I'm in the market for a L3 switch. I'm interested in WS-C3560G-24TS-E or WS-C3560G-24TS-S. I won't need the features that "IP Services" offers for the time being however the time might come where I will need the functionality it provides over "IP Base". My question is, if I purchase a WS-C3560G-24TS-S will I be able to install the "IP Services" image at some point? I'm assuming I'll have to purchase a license but will the hardware I have work? Or when I purchase the license will I be provided with some sort of module I install to upgrade it to the WS-C3560G-24TS-E model? TIA.