Interview process...is this a good sign? Salary negotiation?

Hi guys,

For the past 3 weeks I've been interviewing with a local software company. It's one of the fastest growing companies in the city with < 30 employees, but will most likely double in size within the next year.

My first interview was with the CEO and that went well. It's a sales position, so I made sure to ask alot of questions and try to close him at the end, which he seemed to appreciate. He said that he was really impressed, but we should go through the proper channels and setup a meeting with him partner(cofounder/CTO) for the following week.

The meeting with the partner went well. I again tried to close him, but he said ultimately the decision would be up to the CEO. I asked if he'd hire me if it was up to him, and he said yes So again, looked promising.

The next day I got an email from the CTO(in response to my thank you email), thanking me for the meeting and saying that he forgot to ask me, but what are my salary expectations. I replied that salary is important, but it was most important for me to find a position that is a good fit for my skills and interests. I also said I would need more info about the commission structure and other benefits before I could come up with a figure, but that I was confident they would make me a competitive offer and asked what budget they had set aside for the role. The CEO replied back and said next steps would be 3 references.

I provided most my recent CEO, a past CEO, and a past colleague. So far they've only spoken with my colleague(who gave me a great reference), and they told him that in the past 2 years, they've interviewed about 50 different people for various roles, but they were most impressed with me. The CEO emailed to say that he would be speaking with my other references in the next few days, but asked me if I when I would be available for a phone chat this week.

This all happened last week, and the phone chat is set for tomorrow morning. I'm just curious as to what it might be and how I should prepare. Could this be a verbal offer or another round of questions? Any advice and how to handle a salary negotiation if it comes up? Thanks.

Regards,
Chad