My experience with Mintex is that 1155 need a few good stops to get the heat into them before they work. From stone cold in the morning they are useless. Mintex 1144 work better from the off but dont offer as much fade resistance as 1155 on track. Neither of these pads will ever fade on the road. Both squeele badly and produce lots of brake dust but they are reasonably cheap.
Pagid make some really good pads for the Impreza but are very very expensive. The Ferodo DS 2500 is accepted as one of the best aftermarket pads for the Impreza , is 2/3 the cost ofthe OEM Brembo pads and is the one I'd go for. If you are after the best pad and price is not an issue (which I know is not what you asked for but hey if the fit takes ya!) then the Pagid Black - RS4-2-1, which is even more expensive then the OEM Brembo pads on the STI is an exceptional pad.
I put motor factor standard chepo pads on my 280 bhp MY 03 WRX before I sold it in 2007. For the kind of driving you describe they were fine, just so long as you dont expect them to hold up to any kind of hard driving. As always its horses for courses. The more horses you use the better the pad you'll need and with regard to brake pads you get what you pay for so dont expect miracles from cheap pads with extravagant claims.
Frawls