Primarily street driven = SM2 should be fine.
Spending time at the track = Get Turbolink (boost sensing preferred)
SM2 is a killer street tuning tool. Reports most of the data parameters, small, easy to read, easy to hookup and cycles through the data points quickly.
However, at the track you are going to need more data than Min. O2's, Max KR and their associated MPH's. Like MAF, TPS, Coolant Temp, Manifold Pressure and so on. SM2 may report 10 degrees of KR at 105 MPH. What it won't show you is that you were detonating from the 2-3 shift all the way to the 105 MPH spike. Relevant information.
Keep the initial monetary investment in perspective. It's a one-time expenditure, will last for years, and with the cost of a new motor at $3-$5,000 it's actually pretty cheap in comparison.