I'm looking for a 4-line (or more) IP phone that is as close to the Draytek phone as possible and must have at least 16 (ideally more) programmable BLF keys.

I found the Grandstream GXP2110 which looks ok. Anyone used Grandstream phones with the IPPBX?

Any others I should be looking at?

I'm quite happily using Yealink phones. Nice design, alot of programming options. The T26 has 13 programmable keys, the T28 has 16. There are a couple of extension modules to choose from to add additional keys.

Thank you. These Yealink phones look ideal. I like the expansion modules.
But it doesn't say how many lines the phones support. Interested in the T28 model. Says it supports 6 SIP accounts. Do they mean lines?
I'm looking for a phone to have 4-6 lines on one SIP account.

Each SIP account is in the traditional sense a "line". I do not understand what you mean by having 4-6 lines per SIP account.

On the Draytek IP phone, you just add one SIP account, but then you have two lines. i.e. you can have two concurrent calls in progress. Typically this is to allow you to park a call and then pickup the second line to make it's transfer connection.
I want a 4-line or 6-line phone to allow the user handle more calls and have more than one call on park.