The things you like in the Gerber, you'll have to pay more for in a Spyderco. The Spydies are built for function, so "feeling solid" is less important than "being solid". For example, I finally replaced my Harsey with a plastic-handled Delica. It's every bit as tough as a knife needs to be, but it doesn't "feel" as strong or rigid. You can get a steel-handled Delica or Endura at around a $50.00 price point, but that won't feel as grippy as the Harsey. To get that kind of grip and solididy, you'd prolly have to upgrade to the Military or Paramilitary, which're awesome knives, in my opinion.
Thing is, Spyderco just doesn't really make a knife like the Harsey. Almost all Spydies are "bent" slightly in the handle, to give you a more ergonomic grip in the hand. Now that I use 'em almost exclusively, the Harsey surprises me with its "straightness" when I open it.
The things that make Spyderco knives stand out are almost entirely "under the hood". The blade steels, grinds, denser than average G10, and deceptively simply but ungodly strong locks don't _look_ cool, but they work like you wouldn't believe. Their knives often have blades that look too small for their handles, but the knife works better than if they'd pushed the blade longer or the handle smaller.
Now, I've been using Spydercos for a coupl'a years now, and I've invested quite a bit in 'em (by my standards ;D ), but I still think the Gerber Harsey feels like a high-quality knife. So it's not just you

You could very well stick with it for a very long time and be totally satisfied. If you do decide to upgrade, I'd strongly recommend the Paramilitary. It's prolly my favorite Spyderco overall right now, and it's also the closest I've handled to the Harsey. The blade's the same length, and the handle's about 3/4" longer. I find it much more comfortable (like the Military, I had to "give it a chance" before my hand figured out how to like it), and the full-flat-ground S30V blade cuts like nobody's business. The second-best one-handed cutter I've used.
My only other suggestion would be the Spyderco Sharpmaker. If you don't know how to sharpen, you'll learn in about a half-hour flat with the Sharpmaker kit. It's really worth it to always have a sharp knife handy.