Hello Arne,
My name is Dmitry and I've been working with a team of professionals since 2006. We've implemented many complicated projects and will be happy to solve your tasks.
Talking about budget and timeline I can tell you real price only after we will discuss project in details and I'll create use-cases. I could talk you real price only on use-cases because I would count billed hours for the project.
We're working with such work process:
1) discussing project and create use-cases;
2) dividing use-cases into logic modules and sprints;
3) work on each sprint and showing result after finishing each of them;
4) showing full done result.
In our work we use the-state-of-the-art technologies: HTML5, CSS3, bootstrap, less, AngularJS, CoffeeScript. We work with most modern frameworks: Symfony, Yii, Kohana, Ruby on Rails.
We have deep experience in work with MySQL, PostgreSQL.
In our work, we use JIRA, Git, and many tools like capistrano, webpack, etc. In case we have a corresponding budget, we use unit and integration testing.
Our team works with such agile methodologies as scrum and XP.
Please let me know where we can get the project description to discuss the details.