Power consumpution is huge in the field. So I would take some tests on your tascam to make sure it can handle it. But another thing to consider is, will it brick wall with spls at a live concert. I don't know, but its worth a shot. Some general advice would be this
1. Your mics have the greatest impact on your sound. Spend money on mics first and foremost. However if you can get by with your mics try taping for a while and see if its your cup of tea. If it is then think about upgrading
2. Nomad Jukebox 3 is your friend. $150-200 portable recorder. Don't have to worry about laptop in field.
3. UA-5. I guess these are discountinued, but find one on ebay and it can be modified to be an awesome preamp/analog digital converter. $200-300
4. If you go to concerts where there are other tapers, get a clamp
5. If not, buy a stand from amvona on ebay less than $20
6. Don't forget about the little things, t-bar, windscreens, cables, extra batteries, gear bag. it all adds up.
7. enjoy it. pm me if you need more help