Actually they do help. The big performance hit when you run out of RAM is because the OS starts swapping memory pages to the drive. On a HDD, this means your memory access speed goes from around 15 GB/s to 1 MB/s (for a 4k memory page). A 15,000x slowdown. With a SSD it goes from about 10 GB/s to around 200-300 MB/s, or only a 50-75x slowdown. It's much less noticeable than hitting the pagefile on a HDD (hundreds of times faster than a HDD).SSDs are great if you're coming from an HDD but wouldn't really 'help' when you run out of RAM.
When I first got a laptop with a SSD, it came with only 4 GB of RAM. I ordered an extra 4 GB module, but it took about a week shipping. I ran Photoshop on it and regularly had 6+ GB of RAM allocated. The performance hit was much less noticeable than doing the same Photoshop tasks on my previous system (4 GB and HDD). The computer stays responsive even though it has exceeded RAM and is swapping to the pagefile. And when the extra RAM arrived and I went up to 8 GB, the improvement wasn't very noticeable.
The only real concern is putting additional wear on the SSD from hitting the pagefile so often. But if you're normally at 80% RAM usage then it won't happen that frequently (I was regularly over 100% RAM usage). Just make sure you get a 250+ GB SSD.
As for RAM vs SSD in this case, I'd say it depends on what you're doing. One of the huge benefits of a SSD is that it can handle multiple I/O requests simultaneously without breaking a sweat. A HDD will bog down from a single I/O request - this is why a HDD computer pretty much becomes useless if there's a virus scan running in the background. With a SSD you can run a virus scan, a malware scan, copy your entire MP3 collection, and play a movie file all at the same time, and the system will still start a new program almost as quickly as if none of the other tasks were going on.
So if you're doing stuff with the computer which accesses the HDD a lot, then I'd say get the SSD first. If you tend to just run one program at a time and are encountering slowdowns because it (alone) is pushing you past 8 GB of RAM use, then get the extra RAM first.