Depends on your budget! DS4s with ATX 40 are the cheapest, but hose routing is OK, rather than great. All regs, other than the "dive centre package" ATX40s are now XTX. DSTs with the new hose on the end are also good. If you are feeling more flush, the XTX 200 or the Tec 3 has very nice hose routing for twinsets.
Well done on your choice of Apeks over Poseidon - much better regs, simpler, better value and less to go wrong. How Poseidon got away with the different colours for different gas X-Tream bullshit is beyond me.
I have more than a dozen Apeks (DS4, DST and ATX 200) and am delighted with them.
Lanny
“My deepest and longest dive was over 50m for 3 months, but I was wearing a nuclear submarine at the time.”