You dont gain power by simply installing Ti valves and HD springs. One place where you would get the gain is that the Ti valves and HD would let you run a more aggressive camshaft. With lightweight valves and stiff springs there is less reciprocating/moving mass. Valve float will be reduced and one could poss have a higher red line as well..
The engine should also spool up a bit faster which I think would help. It might not increase your peak hp but it would sure feel faster because it would reach the peak hp number faster. I'm not 100% sure on that however.
Titanium is used to lower weight which in theory would lower neccesary spring pressure to close the valve being opened. Bikes that use titanium now do so for several reasons. A) they are minimizing area and need to be able to use a single spring instead of a dual spring set up. B) They are spinning the engine faster which dynamically increases the weight of the valve and so on and so on. The benifits of switching to titanium would only be being able to lower spring pressure in a stock bike which would give back some cranking losses the engine incurrs just running. But if you bought stainless it would still be lighter than most stock valves. and cost about 1/4 of the price. Then you could afford the nice spring set and the Ti retainers and a set of cams. If you use cams that need such a set up you will also need high compresion pistons to allocate valve to piston clearance and make up for some of the compression lost due to the increased overlap of the cam. Now the tricky part is to not get caught up in the crap everyone tries to sell. If you buy a pipe that advertises 7hp gain then some cams that advertise 8hp gain and some pistons that are around a 3hp gain, it does not mean you get 18hp. I would expect in the range of 10-15 at most. I built superbikes for a living and I will tell you, the bikes of my career era were 750's making 145-160 hp. and those motors cost about 25k to build the first time and the most expensive part was the machine work and labor needed for such attention to detail. Ten minor upgrades might give you 3hp and the next 3hp might need 25 processes to achieve.