Are there any specific features you require from the SRX line-up? i.e. UTM features or Web filtering.
If all you need is just simple firewalling and multi-port routing, you might want to obtain a Cisco ASA or ISR instead. Probably a lot easier to get paid (re)configuration support from outsourced vendors or freelancers than with Juniper products.
I had a short experience configuring an SRX240 for a customer and all I can say is that interface is too convoluted. It would only work if I ran the initial wizard following a factory restore.
Trying to manually configure the additional features required (simple 2 subnets individually NAT to 2 WANs) would fail rather spectacularly regardless of whether I used the GUI or CLI.
Furthermore, the web-access filtering refused to stop functioning even though I had disabled the feature and started blocking every website we came across.
We eventually gave up and I configured an old SSG20 (and reconfigured the ISP's ISR2921) to takeover the duties until we could retrieve an old PIX loan unit from the sister company.