Hi Sjose
You don't really have feature sets as such with Pix506E. You just need to buy a pix 506E and then you can have a free upgrade to a 3DES license which involves obtaining a key from the Cisco web site and loading it onto the pix. Or you can order the pix 506E with a 3DES license on it.
From the cisco web site
==================PRODUCT ORDERING INFORMATION
Table 2 lists ordering information for the Cisco PIX 506E security appliances and related products.
Table 2. Ordering Information
Product Number
Product Description
PIX-506E PIX 506E Chassis (chassis, software, 2 10/100 interfaces)
PIX-506E-BUN-K9 PIX 506E 3DES/AES Bundle (chassis, software, 2 10/100 interfaces, 3DES/AES license)
PIX-506E-PWR-AC= Spare AC power supply for PIX 506E
PIX-VPN-DES PIX DES VPN/SSH/SSL encryption license
PIX-506-SW-3DES PIX 506/506E 3DES/AES VPN/SSH/SSL encryption license
===========================
HTH
Jon
