I'm assuming its only a 1.5L engine. That's pretty small so I'm not at all suprised that you feel a lack of power.
I had a '93 Sentra Classic (B12)
Mom's got an '03 Altima 2.5S
Dad had a '98 Sentra GXE
Current "rides": 2000 Kona Caldera "Callie", 1996 Specialized Hard Rock "Betty"