Lot of ways to get it done, I specifically suggested the 430w/106b combo because he said he was working on his “ticket” I assume that to be his instrument ticket and if he wants to take his check ride in his 150 the 175 alone will not work. The 430w/106b combo will work and allow the require diversity of approaches to be flown................
Sorry, I misunderstood your complete reason for the 430w, which I assume is that the 430w also includes NAV/COM. And yes, that would be a great option to get everything, but the labor cost is still there. Also, I haven't research aftermarket repair options for the 430w, but Garmin stopped supporting it. It would stink to spend all that $$ for install and then have the unit crap out and be impossible to repair due to lack of parts. However, I guess one could slide in an Avidyne unit???
The dilemma with the Garmin gps 175 or GNC 355 of GNX 375 is that you don't get the NAV. But how useful is the NAV? Or keep the MX300 and find the needed exta pieces off ebay for $200 total and get a nav/glideslope and go with GNC355.
For all the GPS navigators you will also need either a CDI or a GI275 or an HSI (hopefully AV30 HSI gets certified soon). This is the big decision I am having now, see my other threads. I think it may be cheaper to buy another airplane, lol