Carlos,
The difference between the 3c and 3cxl is not just the extra RAM but also more TCAM. It is therefore not field upgradeable.
Regards,
Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México