Get a 5701. It's the top Viper without any stupid crap like the LCD remote or anything. 2 way, alarm, remote start. Keep in mind, depending on the vehicle you might have a lot of extra cost in modules you'll need for factory systems (immobilizers, factory alarms, etc.) and vehicle specific things (door locks, etc.) And then depending what other options you want (digital tilt switches, prox sensors, glass sensors, trunk pop, backup batteries, extra sirens or piezos inside, etc.) you might be looking at a few hundred bucks over the base price of the alarm/rs system. A basic alarm system can be a good deterrent, but if you're really worried about people jacking your shit, adding all the extra stuff gets expensive real fast.
I've got a digital tilt switch and will be getting a prox sensor whenever I get off my lazy ass and buy it. I'm big on the deterrent aspect of it, so to me the prox sensor is a way to make sure that people realize I've got an alarm on it, and that they're better off just going to the next car. I don't think there's much actual security benefit of prox sensors outside of that unless you've got a cloth top. If you're looking to actually protect what's inside the vehicle, glass sensors, piezos, extra sirens,and maybe a backup battery siren or 2 are your best friends. A single piezo is extremely annoying. A group of piezos going off is probably harmful, and with enough of them it might be possible to actually incapacitate someone. especially if you had a way to create very bright light flashes, like super LEDs or something (basically simulating the effect of a flashbang).
The nice thing about Viper is that DEI does their best to make sure that all those add ons that really make the alarm are easily integrated, and they make all those accessories.