I use sipgate and sipdroid together, without any in between such as pbx.org or sipsorcery, or any of those. Here's my relevent settings in sipdroid:
For SIP Account settings:
username/pw
Server set to sipgate.com
Domain left empty
Username/Caller ID left empty
Port 5060
Protocol UDP (I don't think sipgate supports TCP, or at least they didn't used to. If you really wanted TCP for better battery life, you'd need to go through something like sipsorcery or pbx.org)
Audio/Video Settings:
Earpiece gain High
Mic Gain Medium
Headset Gain Medium
Headset Mic Highest
Video Quality High
Audio Codecs settings:
G722 HD Voice, Only over WLAN and 3G
silk24, Never
silk16, Only over WLAN and 3G
silk8, Always try
PCMA, Only over WLAN and 3G
PCMU, Only over WLAN and 3G
Speex, Always Try
GSM, Always Try
BV16, Always Try
Advanced Settings:
Use Stun Server, Unchecked
Think those are the only relevant ones for my setup. If you're shooting for the same kinda setup, then maybe trying some of those settings might help. I assume that you're firewall at home isn't blocking SIP right?