CRM Evaluation

We are a small organization with our management and administrative side run only by volunteers. We have approximately 70 members, have received one grant, and have many (small amount) individual donors. We have a button on our website where members can sign up and pay and that exports to an excel sheet. And "excel sheet" is the extent of our donor management! We are small enough and can so far do things manually. More, we do not to burden our brains nor our wallets with over-complex CRM systems at this point. But we also want to be sure we are being responsible stewards of membership, and be open to when its time to change. So from this session, we would like to have a discussion with someone knowledgeable on CRMs, but also on small-but-growing organizations. So we would like to:
1) discuss / learn (for example, most urgent and important features of managing members / donors)
2) figure out if we already need a system, or if we should stick to manual for the moment
3) if it is determined that we already need one, have someone help us look at some appropriate models for our size and teeny tiny budget
4) if it is determined that we do not need one yet, have someone help us develop "tripwires" that will indicate at what point we should revisit the topic (example: 100+ members? 100+ donors? certain size of budget or award? etc)