I am trying to stretch my photography budget, but am looking at tripods. My basic question(s) are as follows:

I currently have a Velbon tripod very similar to the one in the link below.

Amazon.com: Velbon DF-60 Dual Function Light Weight Tripod: Electronics

The legs and construction appear to be reasonably substantial, so I am thinking of just replacing the head right now and following up with a new leg set later on.

The heads I have been looking at are below:

Amazon.com: Manfrotto 498RC2 Ball Head with Quick Release Replaces Manfrotto 488RC2: Camera & Photo

Amazon.com: Manfrotto 322RC2 Joystick Head Short: Camera & Photo

So, my questions are:

1) Good idea/bad idea to do what I am thinking of?

2) Better choice for head?

EDIT: I probably ought to list my normal kit that I would use with the above tripod

Nikon D5000
18-55 VR, 55-200 VR, 70-300 VR, 35 f1.8 and soon (probably late Aug) Tokina 11-16 f2.8
SB400