The HTA 67 is not a massive improvement over a regular 67. Keep the 67, everyone with bigger setups are moving back to it as THE setup to run. Bigger means way too much lag, inconsistancy, and not as much fun. Upgrade to HTA if you want, but otherwise I say just rock and roll on your current setup, maybe switch to E85 or meth injection so you get more out of it daily
As for HTA, it's a billet aluminum compressor wheel. They are also redesigned, smaller wheels that generally outperform and outspool (transient) their predecessor. PTE's new billet wheels are cheaper, sub-performing versions of this.