I’m looking for some reliable 8x or 16x - or + R media for the GSA-H20L.
MCC004 Verbatim 16x - it works brilliantly in almost any modern burner
Your drive is a [I]late 16x generation[/I] drive. This means that the support for YUDEN000 T03 and TYG03 has been implemented (finally, successfully).
Reliable media which your drive will like (in addition to [B]Kev[/B]'s favorite MCC004, which indeed is excellent media):
Taiyo Yuden 8x DVD+R (YUDEN000 T02)
Taiyo Yuden 16x DVD+R (YUDEN000 T03)
Mitsubishi/Verbatim 16x DVD-R (MCC 03RG20) and its predecessors (Verbatim 8x, 4x DVD-R)
Taiyo Yuden 16x DVD-R (TYG03)
Taiyo Yuden 8x DVD-R (TYG02)
There is also some good everyday usage media for your drive like RICOHJPN R03 (only under Ricoh brand), CMC MAG E01 (Imation), MBIPG101 R04 (Imation).
Avoid E-net brands (Ridisc, Rivision, Datawrite, Datasafe, Tuffdisc), those are mostly CMC and Ritek but the quality is too unconsistant.