The answers to this question: Basic Web Development IDE/Editor like Dreamweaver? contains several programming IDE's that may fit your needs but I think that this alternative may be the best for your case: http://askubuntu.com/a/59636/9598. It won't be reproduced right here.
For the case that you need support connecting to the FTP server for upload/download/sync, please refer to the accepted answer on this question on StackOverflow: How Connect to remote host from Aptana Studio 3 which I place here for your convenience:
From the Project Explorer, expand the project you want to hook up to a
remote site (or just right click and create a new Web project that's
empty if you just want to explore a remote site from there). There's a
"Connections" node, right click it and select "Add New connection...".
A dialog will appear, at bottom you can select the destination as
Remote and then click the "New..." button. There you can set up an
That's how you set up a connection that's tied to a project, typically
for upload/download/sync between it and a project.
You can also do Window > Show View > Remote. From that view, you can
click the globe icon in the upper right to add connections and in this
view you can just browse your remote connections.
Additionally, for your needs on a stable/reliable FTP Client I suggest you gFTP, which does a great work to upload/download. A Screenshot is placed here for you to see gFPT in action:
If you need further support don't hesitate to drop a comment.