I personally still recommend x2 4981

It's rock solid stable.. and doesn't have x2 config live like 5032/5035 does.
...and, to me anyways, that's a good thing. I
hate the "X2 config live loading...." screen that you get with the newer x2 bioses. Plus, I only ever set my bioses up once and once I do that I never touch em. Thus, the added boot time due to the bios needing to wait for the hdd to spin up to read the .ini in addition to the (IMO anyways) annoying loading screen negates any benefits it provides.
...and by that same logic, I recommend a customized version of m8plus_16 with live blocking, igr, and lba48 support for 1.6/1.6b xboxen.