My number one regret is buying things that I knew I would upgrade later. I first bought two picnic taps... upgraded in a month, wasted $15. I bought a cheap chest freezer that was too big and only held 3 kegs... upgraded to one that smaller and held five (whirlpool 8.9).
My recommendation, don't buy stuff with the plan on upgrading later. Buy the upgrade now. The only non-regret I have is going with regular faucets instead of perlicks. I found a phenomenal deal on five new faucets for $40 on ebay. However, if I was paying full price, the extra $10 per faucet is probably also.... worth the upgrade.