The SA6 is an IEM I really still want to try. I've used the PFE, and at its price, it's an awesome deal. To step to the SA6, you really have to justify spending an extra $100 which is a sizable step up.
I hold the PFE in high regards because it does a lot of key things very right. It is ultra accurate and effortlessly dynamic. It has great transparency. The frequency response is good, and the filters add some adjustment on this. EQing can however improve upon the end sound and balance out the response. The top end response is a bit ragged and does improve considerably with EQing. Comfort is great with the over-ear design, and you get zero microphonics from the cord doing this. Isolation is great. Build quality is decent, especially for an IEM that was specifically geared as a budget product from a company that makes multi-thousand dollar hearing aids. To build a product as good as it is in the low hundreds is quite a feat. It's not a particularly durable feeling IEM with the plastic casing and simple cord design with no stress reliefs.
Now personal preference will dictate if one option is better then another. For example with the comment of the SA6 having superior bass to the PFE, I would doubt it. I would say it presents the bass differently. The PFE itself doesn't do anything wrong in the bass region. There is a slight EQ hump (+3dB) over the midbass and bass region that provides a full presentation. Notes are effortless and crisp. Frequency response does extend well down to 20-30Hz. It's not sloppy or lacks anything. However, it does sound different then another product. Personal preference will become the determining factor in which is better simply because in terms of raw function, the PFE doesn't fail. However, I like the bass response of other earphones better for personal reasons. I personally like more weight to the notes, clean, but with more body. I like to hear a more evolved attack and decay of a note. The PFE to me is too clean. It's to crisp, too short on note and doesn't give enough time (my preference) to develop the note. Bass and most other notes go as quickly as they come. This is all just personal preference though.
